Remove smoltcp networking

[Weidong Cui (wdcui)]

This PR removes the retained smoltcp and TUN networking backend after brokered IPv4 TCP and UDP become mandatory, simplifying LiteBox networking to broker-owned sockets, deleting the local socket set, packet device, port allocator, and local ring-buffer channels, removing IP packet provider contracts and TUN setup and runner plumbing across platforms, and dropping obsolete local-stack tests while retaining the portable broker-backed tests for the planned test fixture.

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

Click for details

--- failure enum_missing: pub enum removed or renamed ---

Description:
A publicly-visible enum cannot be imported by its prior path. A `pub use` may have been removed, or the enum itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/enum_missing.ron

Failed in:
  enum litebox::platform::ReceiveError, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/platform/mod.rs:260
  enum litebox::net::PlatformInteractionReinvocationAdvice, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/mod.rs:457
  enum litebox::net::local_ports::LocalPortAllocationError, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/local_ports.rs:141
  enum litebox::platform::SendError, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/platform/mod.rs:255
  enum litebox::net::PlatformInteraction, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/mod.rs:432

--- failure enum_variant_missing: pub enum variant removed or renamed ---

Description:
A publicly-visible enum has at least one variant that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/enum_variant_missing.ron

Failed in:
  variant SendError::PortAllocationFailure, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/errors.rs:165
  variant NetworkProxy::Stream, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/socket_channel.rs:190
  variant NetworkProxy::Datagram, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/socket_channel.rs:192
  variant NetworkProxy::Raw, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/socket_channel.rs:194
  variant ConnectError::PortAllocationFailure, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/errors.rs:67
  variant ListenError::NoAvailableFreeEphemeralPorts, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/errors.rs:127

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/inherent_method_missing.ron

Failed in:
  Network::set_platform_interaction, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/mod.rs:495
  Network::perform_platform_interaction, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/mod.rs:505

--- failure module_missing: pub module removed or renamed ---

Description:
A publicly-visible module cannot be imported by its prior path. A `pub use` may have been removed, or the module may have been renamed, removed, or made non-public.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/module_missing.ron

Failed in:
  mod litebox::net::local_ports, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/local_ports.rs:4

--- failure struct_missing: pub struct removed or renamed ---

Description:
A publicly-visible struct cannot be imported by its prior path. A `pub use` may have been removed, or the struct itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/struct_missing.ron

Failed in:
  struct litebox::net::socket_channel::DatagramMessage, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/socket_channel.rs:765
  struct litebox::net::socket_channel::DatagramSocketChannel, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/socket_channel.rs:781
  struct litebox::net::socket_channel::StreamSocketChannel, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/net/socket_channel.rs:339

--- failure trait_missing: pub trait removed or renamed ---

Description:
A publicly-visible trait cannot be imported by its prior path. A `pub use` may have been removed, or the trait itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/trait_missing.ron

Failed in:
  trait litebox::platform::IPInterfaceProvider, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox/src/platform/mod.rs:238

--- failure trait_removed_supertrait: supertrait removed or renamed ---

Description:
A supertrait was removed from a trait. Users of the trait can no longer assume it can also be used like its supertrait.
        ref: https://doc.rust-lang.org/reference/items/traits.html#supertraits
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/trait_removed_supertrait.ron

Failed in:
  supertrait litebox::platform::IPInterfaceProvider of trait Provider in file /home/runner/work/litebox/litebox/litebox/src/platform/mod.rs:29

--- failure struct_pub_field_missing: pub struct's pub field removed or renamed ---

Description:
A publicly-visible struct has at least one public field that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/struct_pub_field_missing.ron

Failed in:
  field local_address of struct AcceptedPlatformSocket, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_broker_core/src/socket.rs:31

--- failure trait_method_parameter_count_changed: pub trait method parameter count changed ---

Description:
A trait method now takes a different number of parameters.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/trait_method_parameter_count_changed.ron

Failed in:
  PlatformSocket::bind now takes 2 instead of 1 parameters, in file /home/runner/work/litebox/litebox/litebox_broker_core/src/socket.rs:277
  SocketProvider::create now takes 4 instead of 3 parameters, in file /home/runner/work/litebox/litebox/litebox_broker_core/src/socket.rs:256

--- failure trait_method_missing: pub trait method removed or renamed ---

Description:
A trait method is no longer callable, and may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/trait_method_missing.ron

Failed in:
  method send_ip_packet of trait HostInterface, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_linux_kernel/src/lib.rs:389
  method receive_ip_packet of trait HostInterface, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_linux_kernel/src/lib.rs:391

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/inherent_method_missing.ron

Failed in:
  LinuxUserland::wait_on_tun, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_linux_userland/src/lib.rs:401

--- failure method_parameter_count_changed: pub method parameter count changed ---

Description:
A publicly-visible method now takes a different number of parameters, not counting the receiver (self) parameter.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#fn-change-arity
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/method_parameter_count_changed.ron

Failed in:
  litebox_platform_linux_userland::LinuxUserland::new takes 1 parameters in /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_linux_userland/src/lib.rs:179, but now takes 0 parameters in /home/runner/work/litebox/litebox/litebox_platform_linux_userland/src/lib.rs:125

--- failure union_missing: pub union removed or renamed ---

Description:
A publicly-visible union cannot be imported by its prior path. A `pub use` may have been removed, or the union itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/union_missing.ron

Failed in:
  union litebox_platform_linux_userland::Ifru, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_linux_userland/src/lib.rs:154

--- failure trait_method_missing: pub trait method removed or renamed ---

Description:
A trait method is no longer callable, and may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-item-signature
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/trait_method_missing.ron

Failed in:
  method send_ip_packet of trait HostInterface, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_lvbs/src/lib.rs:958
  method receive_ip_packet of trait HostInterface, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_platform_lvbs/src/lib.rs:960

--- failure struct_pub_field_missing: pub struct's pub field removed or renamed ---

Description:
A publicly-visible struct has at least one public field that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/struct_pub_field_missing.ron

Failed in:
  field tun_device_name of struct CliArgs, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_runner_linux_userland/src/lib.rs:69

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/inherent_method_missing.ron

Failed in:
  LinuxShim::perform_network_interaction, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-ulitebox/4af049ab6456bf95775ef222a7c408fdde51c58a/litebox_shim_linux/src/lib.rs:331