Don't no-op on resuming top activity if display is in freeform.

Currently, when we try to resume the top activity of the task, we exit
early if the activity is already resumed. However in the case of
freeform display area and multi-resume, it's possible we want to
proceed with the rest of the operation (pausing the back stack based on
visibility check) since multi-resume is possible. For example, in the
case of a maximized app behind a freeform app, when we bring the
maximized, fullscreen app to the front (which is already resumed), we
want to then pause the back stacks since everything is covered up.

Bug: 168852384
Test: atest
PinnedStackTests#testAutoEnterPictureInPictureOnUserLeaveHintWhenPipRequestedNotOverridden

Change-Id: If2dc3f97ca2afd2992c7546e91a36d826cbf9c72