PackageMonitor improvement

The PackageMonitor receives package broadcast events and notify the
registered client with several callback methods. But the delivery of
the broadcast is unpredictable, e.g. broadcast queue is almost full,
the event will be sent to client late.

Try to improve some package events with callback from system instead.
This change still keeps using some broadcast events sent from user
manager and activity manager service.

Bug: 29385425
Test: manual
Test: atest PackageUpdateMonitorTest#startMonitoring_registerOnlyOnce
Test: atest PackageUpdateMonitorTest#stopMonitoring_unregistersOnlyOnce
Test: atest DataManagerTest#testDeleteUninstalledPackageDataOnPackageRemoved

Change-Id: I44727cead739270b63623aeda2c07cb6e7781d36