Refactor reporting activity idle

- Separate the logic of stopping and finishing from idle.
- Correct the condition of stop profiling from idle.
- Remove the resuming of focused stack if an activity is
  removed while idle, because if idle is scheduled or reported,
  the next focused activity should be ready to show, then the
  resuming from background destruction is a no-op.

Bug: 130340090
Test: atest ActivityLifecycleTests

Change-Id: Iabccc26f40c8cbccb8e4a260d8aff84322193f2b