Call `conn.send_failed` if `stream.send_all` fails with an exception.

[GalaxySnail]

See details:

[1] https://trio.readthedocs.io/en/latest/reference-io.html#trio.abc.SendStream.send_all [2] https://h11.readthedocs.io/en/latest/api.html#h11.Connection.send_failed