Add locus id to ActivityRecord / TaskInfo

- Bubbles needs to know if a task has a LocusId for the
  Suppress Bubble API
- Apps can already set a locusId on the activity, this
  occurs after the activity has been created.
- This CL adds the locusId to the ActivityRecord and
  triggers a task info change
- TaskInfo uses the top activity in the stack to populate
  the locusId

Bug: 170267239
Test: atest NotificationManagerTest (in CTS CL)
Change-Id: I33cf784e3f3f89835d91e31961b3abe7a7b68c8d