Check precise resumable state for task overlay

The top activity on task may be INITIALIZING state but it might be
able to resume after its process is attached. So check the focusable
state and hierarchy visibility instead.

That avoids mDoResume from being set to false for a top activity.

Bug: 352423986
Flag: EXEMPT bugfix
Test: Launch an app which will show notification permission activity.
      Return to home and kill process of permission activity.
      Launch the app again. The permission activity should resume.
Change-Id: I2ff64e9facefd6cbb89a30e161c742af3393d2be