refactor(iroh-net)!: remove the magicsock module from the public api

[divagant-martian]

Description

magicsock main's component, the MagicSock is not useful on it's own. Having it on our public API forces us to treat as breaking changes modifications that for a MagicEndpoint user are implementation details. To avoid this, this PR makes the following changes:

• expose all types that are part of the public functions of the MagicSock as pub use
• explicitly re-export every publicly exposed by magicsock from magic_endpoint (so that the types involved in the prev change can be used from magic_endpoint directly)
• changes the description of the magic_endpoint module to not include the MagicSock and make it more expressive at the same time.
• MagicSock had a bunch of methods that were simply methods of Inner re-exposed. Now that MagicSock is private, we can get rid of those all and simply use Deref to Inner without exposing Inner via trait associated types.
• That being said, renames MagicSock to magicsock::Handle which is what it really is, leaving only the new and close methods, which are the ones that handle creation and destruction of the associated tasks.
• Misc rename of fields of type MagicSock to msock, which I think aligns better to new naming as is more readable/clear.
• Simplifies the Timer code. The removed parts were considered used because they were publicly accessible. Becoming private showed parts that were dead code.
• local_addr no longer returns an error (it seems to be it never did), but it became more clear in the process of accessing the MagicSock(Inner) methods via Deref.
• MagicEndpoint::local_addr no longer returns an error

Breaking Changes

• module magicsock is no longer public
• iroh_net::magicsock::ConnectionType -> iroh_net::magic_endpoint::ConnectionType
• iroh_net::magicsock::ControlMsg -> iroh_net::magic_endpoint::ControlMsg
• iroh_net::magicsock::ConnectionInfo -> iroh_net::magic_endpoint::ConnectionInfo
• iroh_net::magicsock::ConnectionTypeStream -> iroh_net::magic_endpoint::ConnectionTypeStream
• iroh_net::magicsock::DirectAddrInfo -> iroh_net::magic_endpoint::DirectAddrInfo
• iroh_net::magicsock::LocalEndpointsStream -> iroh_net::magic_endpoint::LocalEndpointsStream
• iroh_net::magicsock::MagicSock no longer accessible. Use MagicEndpoint instead.
• iroh_net::magicsock::Options no longer public. Used internally only.
• iroh_net::magicsock::PacketSplitIter no longer public. This is an implementation detail of internal use only.
• iroh_net::magicsock::Timer no longer public. This is an implementation detail of internal use only.
• iroh_net::magicsock::UdpSocket no longer public. This is an implementation detail of internal use only.

Notes & open questions

ended up using cargo public-api -p iroh-net diff to get what was added and make some of those not-for-public enums and structs private again. While really useful, checking this is very annoying. Hopefully we don't have to do it often.

Change checklist

• Self-review.
• Documentation updates if relevant.
• Tests if relevant.
• All breaking changes documented.

[rklaehn]

I don't have time for a thorough review, but I very much agree with this, if only to reduce the confusion when talking about MagicEndpoint and MagicSocket.

ended up using cargo public-api -p iroh-net diff to get what was added and make some of those not-for-public enums and structs private again. While really useful, checking this is very annoying. Hopefully we don't have to do it often.

Didn't know this. Nice!

[dignifiedquire]

one change please, other than that LGTM