VoipCallMonitor updates; stopFGS when notifs are removed

VoipCallMonitor was failing to revoke foreground service delegation if
the user dismissed an ongoing call notification for an active call.

This change ensures FGS is revoked if an application does not have a
notification indicating an ongoing call is active.

Fixes: 286090019
Test: 2 new unit tests + manual testing
	- verified an app can update a notif from incoming call to
          an ongoing call and maintain FGS
Change-Id: Iabc60e9616d4cfaf78cad7d10c601d9593543ee0