- Adjust pollset during connection shutdown.
- Separate the FIRSTSOCKET and SECONDSOCKET check so that one being in
connect or shutdown no longer adds poll events for the other.
- Fix shutdown state evaluation (as detailed below).
- Add a unit test for Curl_conn_adjust_pollset.
- Add a client for event testing.
- Test that shutdown sockets stay with the socket callback until done.
The pollset predicate now reads the connection's own shutdown state
rather than going through data->conn, and the EXPIRE_SHUTDOWN arming in
cshutdn_perform() works again: next_expire_ms started at 0 and could
never be set, so a peer that never sends a close_notify would still park
its connection forever, timeout or not.
Reported-by: pszemus@users.noreply.github.com
Fixes https://github.com/curl/curl/issues/22282
Closes https://github.com/curl/curl/pull/22304
