Add Usage Reporting Api to UsageStatsManager

The Usage Reporting Api allows apps to report usage within the app to
platform. Apps with the the OBSERVE_APP_USAGE permission may register
observers that use the reported in-app usage.

Test: manual (using the included Usage Reporter App)
Test: atest CtsUsageStatsTestCases:UsageReportingTest
Test: atest FrameworksServicesTests:AppTimeLimitControllerTests
Bug: 112486938

Change-Id: Iddd6f0993bbbf68a2032b34d473ef8d67da7747a