General clean-up of the single stream connections code

[tomaka]

This PR is a general clean-up of the single stream connection code. It fixes many small issues, and also handles the shutdown phase more properly.
We now properly handle incoming GoAway frames, and have the possibility to send some.

Can be reviewed commit by commit.
I understand that this code is generally extremely complicated, but I don't really have a good solution for this. Networking code is extremely complicated, both in terms of logic and implementation.
Maybe a solution is tests, such as #2323, but at the moment the code isn't even robust enough to have tests.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       +3293 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::incoming_data::h432ddb31867d1fee
       +3229 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::read_write::h8bc962f1048ef9a9
       -2730 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::read_write::h4b1d75277ce755e1
       -2406 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::incoming_data::hc1836819eeefbb99
       -1563 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::process_substream::h5f516992aa8a0a17
       +1554 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::process_substream::h1e796161cd63010f
        -530 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::pass_through_substream_event::hc43f42015d980d3f
        +528 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::pass_through_substream_event::hd7154870b9c37e2b
        -522 ┊ <core::iter::adapters::chain::Chain<A,B> as core::iter::traits::iterator::Iterator>::next::h50bfef632128dec7
        +522 ┊ <core::iter::adapters::chain::Chain<A,B> as core::iter::traits::iterator::Iterator>::next::h6193fd0dcdf3312d
        +477 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::open_substream::hcba77af0193c9e3a
        +459 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::queue_data_frame_header::h67ccb95347510e80
        -438 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::accept_pending_substream::hf251be31074226e5
        +436 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::accept_pending_substream::h3f3f4be70ece2aee
        -430 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::open_substream::ha9ae355068a4b7cb
        +424 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::queue_window_size_frame_header::he9f07d66b1a928cc
        -413 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::queue_data_frame_header::h865540b3b0c3c286
        +405 ┊ smoldot::libp2p::connection::yamux::ExtractOut<T>::next::ha5720afe78453ceb
        -386 ┊ smoldot::libp2p::connection::established::single_stream::SingleStream<TNow,TRqUd,TNotifUd>::update_all::h5a98aac5e74ec89c
        -385 ┊ smoldot::libp2p::connection::yamux::Yamux<T>::next_dead_substream::hd1577e5cd7f201c3
        +267 ┊ ... and 85 more.
       +1520 ┊ Σ [105 Total Rows]

[melekes]

👍