Add tracing for UserState and a few services.

Both BackupManager and AppWidgetManager internals are taking a long
time to process user unlock events, so add tracing details.  Also add
general tracing to show all UserState changes.

Bug: 32859180
Test: builds, boots
Change-Id: I82f4f7220ccb695941acd6bc45cd67a5fae8a4d2