Scope

Ensure mongoc_stream_timed_out returns true for TLS write timeouts

Background
Quoting mongoc_stream_timed_out documentation:

Returns: True if there has been a network timeout error on this stream.

However, this does not appear to be consistently true for TLS stream write timeouts. See:

• _mongoc_stream_tls_secure_transport_write
•  _mongoc_stream_tls_openssl_write
•  mongoc_secure_channel_write

The fix may benefit from the new timed_out field proposed in CDRIVER-6187:

if (write_ret < (ssize_t)buf_len) {
   tls->timed_out = true; // Indicate a timeout
   mongoc_counter_streams_timeout_inc();
}

But I am unsure how to test TLS write timeouts.