This introduces a new sampling state-map for expired connections to fix
segfaults that previously occured when passing in a `connection` record
to `Reporter::conn_weird()` for which the internal `Connection` object
had already been expired and deleted. This also introduces a new event
called `expired_conn_weird`, which is similar to `conn_weird`, except
the full `connection` record is no longer available, just the `conn_id`
and UID string.
