Use flags to indicate reason for Uri changes.

As part of MediaProvider becoming a Mainline module, some partners
need to understand more details about what triggered a Uri change
notification.  This helps listening apps avoid making expensive and
race-condition-prone calls back into MediaProvider; typically when
they're only interested in insert and delete operations.  This change
uses the existing "flags" argument to communicate the reason.

This change adds overloads to ContentObserver for listening apps to
receive these flags.  In addition, we add overloads that deliver a
clustered set of multiple Uris together in a single Binder transaction
to improve overall efficiency.  (This matches well with the existing
CR.notifyChange() API that we added earlier this year, since they
both work with Iterable<Uri>.)

Tests to verify that we only collapse Uris together when all other
method arguments are identical.

Bug: 147778404, 144464323
Test: atest CtsDatabaseTestCases
Test: atest CtsContentTestCases:android.content.cts.ContentResolverTest
Test: atest FrameworksServicesTests:com.android.server.content.ObserverNodeTest
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: I0bbd8a8b4a898ab6f891d085de0ecb4d68cbe302