test: that 2nd protocol.write() to closed socket fails

[0xB10C]

As TCP is buffered and asynchronous at the OS level, the first protocol.write() to a closed socket can succeed for both sync and async. The second write will fail.

As this confused me in #161, and I assumed it's a bug, document this here by having test coverage for it.

closes #161

[0xB10C]

Draft as the first commit is from #163. Will rebase once that's merged.

Also, I don't think having this is super important. Feel free to close if you'd rather not have it.

[0xB10C]

As TCP is buffered and asynchronous at the OS level, the first protocol.write() to a closed socket can succeed for both sync and async. The second write will fail.

Well.. at least on Linux I guess. Not on Windows?

Writing to the closed socket for the first time should succeed.

thread 'pingpong_with_closed_connection_sync' panicked at protocol\tests\round_trips.rs:243:10:
first write to closed socket should succeed!: Io(Os { code: 10054, kind: ConnectionReset, message: "An existing connection was forcibly closed by the remote host." }, RetryV1)

[0xB10C]

Going to close this. I did a few runs in https://github.com/0xB10C/bip324/actions/runs/20881650088?pr=4 and this seems brittle. I don't think it's important enough at the moment. Just be aware that writing to a socket and getting Ok() might not mean that socket is still alive.