[Call Screening]Handling Package Uninstall

Rename PhoneAccountBroadcastReceiver class into
AppUninstallBroadcastReceiver. Detect the scenario
where the default call screening app gets uninstalled
and remove it as the default call screening app,
once happening, set default call screening as "null".

Bug: 116758854
Test: create two call screening applications, set them to default
and uninstall, observing the default call screening is null or not.

Change-Id: Idb2f4bd5da0a20ebaa4f1c77ea9349c8c30a8c17