Erase the const generics from the edge-nal-embassy types

[ivmarkov]

The purpose of edge-nal-embassy is to provide implementations for the edge-nal traits on top of embassy-net.

Therefore, the expectation is that the public struct types of edge-nal-embassy for TCP/UDP sockets would rarely be used and instead - the user would write their code against the edge-nal traits to achieve platform independence.

Nevertheless - and especially if some of these types need to be put in a static context with embassy's make_static! / mk_static! macros - the fact that the edge-nal-embassy types are so heavily generified with const generics is inconvenient, as the user has to type the full types, with their N, TX_SZ, RX_SZ, M generics.

This PR is erasing all of the const generics (coming from the TCP/UDP buffers' pool) by using not the Pool type but rather, a new sealed DynPool trait which - furthermore - is injected in the Tcp/Udp types and their sockets as a &dyn trait (hence its own type is also erased).

As a result, Tcp/Udp/TcpSocket/UdpSocket have now all their const generics removed and have just a single lifetime generic.

Additionally, Tcp , Udp and Dns are now Copy just like the underlying embassy-net Stack type for extra user convenience.

[Copilot]

Pull request overview

This PR refactors the edge-nal-embassy crate to remove const generics from its public types (Tcp, Udp, TcpSocket, UdpSocket, etc.) by introducing a new trait-based abstraction DynPool that uses dynamic dispatch. This makes the types easier to use, especially in static contexts with Embassy's make_static! macros. The PR also makes these types Copy and Clone for user convenience, matching the underlying embassy-net::Stack type. Additionally, it adds comprehensive documentation to the edge-nal-std crate.

Key changes:

• Introduced sealed DynPool trait with dynamic dispatch to erase const-generic pool parameters
• Refactored socket buffer management to use token-based allocation with type-erased pools
• Added Copy/Clone derives to Tcp, Udp, Dns, and Stack types for easier usage
• Enhanced documentation across both edge-nal-embassy and edge-nal-std crates

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
edge-nal-embassy/src/lib.rs	Introduces DynPool trait with sealed implementation, makes Pool public, adds helper function docs
edge-nal-embassy/src/tcp.rs	Removes const generics from Tcp/TcpSocket, uses DynPool for buffer management, adds comprehensive documentation
edge-nal-embassy/src/udp.rs	Removes const generics from Udp/UdpSocket, uses DynPool for buffer management, changes default buffer sizes, adds documentation
edge-nal-embassy/src/dns.rs	Adds Copy/Clone derives and documentation to Dns type
edge-nal-std/src/lib.rs	Adds Copy derive to Stack and Interface, enhances documentation for public API
edge-nal-embassy/CHANGELOG.md	Documents the const-generics erasure and Copy trait additions
edge-nal-std/CHANGELOG.md	Documents the API documentation and Copy trait additions

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