Much like we already do in the `._iter_packets()` async-generator which
delivers to `.recv()` and `async for`, handle the `''[Errno 32] Broken
pipe'` case that can show up with unix-domain-socket usage.
Seems like the cause is due to how fast the socket can be torn down
during a registry addr channel ping where,
- the sending side can break the connection faster then the pong side
can prep its handshake msg,
- the pong side tries to send it's handshake pkt via
`.SocketStream.send_all()` after the breakage and then raises
`trio.BrokenResourceError`.
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