Implement SESSION_TRACK_GTIDS

The session tracking mechanism of MySQL has a type called SESSION_TRACK_GTIDS. This type contains the latest GTID event generated by the session.

The documentation on the protocol level implementation appears to be relatively sparse but this page describes some details. The source code of the MySQL C connector appears to show that the event consists of two length-encoded integers (total length of the changed entity and GTID encoding specification code) followed by a length-encoded string. Implementing the same layout would retain connector compatibility.

The end-user configuration can probably follow the MySQL implementation found here.