An api to query usage events for the caller

Added an api which apps can query to find out about their own usage
events. This is useful in understanding the apps historical bucket
changes.

Test: atest android.app.usage.cts.UsageStatsTest#testQueryEventsForSelf

Fixes: 71906213
Change-Id: Ie6144cfe515fd0748a317835918a9d8cf1aea007