Do full connector tracker cleanup when the session lock is released (#9707)

Do full connector tracker cleanup when the session lock is released (#9707)

As there is no "request end" call after invoking UI.access() from a background thread,
the connector map was not earlier properly cleaned afterwards. If you toggled visibility of a
component from the background thread, the tracker state became inconsistent.

If this becomes a performance problem, it could probably be optimized to that cleanup
is done in request end and only at the end of access if not inside a request.

Fixes #9654