Basic changes to the LocationTimeZoneProvider API

These changes have been broken out as they stand alone and should be
relatively uncontroversial.

The LocationTimeZoneEvent is having UserHandle added, mostly for
logging at this point so we can debug issues with multi-user providers.

Bug: 152744911
Bug: 149014708
Test: atest services/tests/servicestests/src/android/location/timezone/LocationTimeZoneEventTest.java
Change-Id: Iafbd5bc9778d68bc9c3046244e7dca6d9892519e