Removed dependency on using sql_run_id to detect slave reset.
Backported server binlog_relay_io_observer callback interface
from 8.0 for monitoring startup of replication applier.
This makes it possible to detect slave start/restart without using
sql_run_id.
Removed call interface to read server sql_run_id.

Reviewed By: Frazer Clement <frazer.clement@oracle.com>