Prevent IndexOOB when handling app crash

1. Destroy the activity from WPC vs. traverse the wm hierarchy
2. Do not remove the parent task while removing the child task.
   The parent task should be removed once the child is detached
   from the hierarchy.
3. Skip duplicated wm_task_removed log.

Bug: 234214939
Test: wm presubmit
Change-Id: Ia5745ba4df949d62a6cde02555fa5314ced4774e