Make WC#applyAnimation can apply on Task / TaskStack layer (3/N)

Correct isAnimating check in ActivityStackSupervisor
to fix when enabled hierarchical animation, the app launching remote
animation can't work for the 2nd launch because
activityIdleInternal -> schedule StopActivityItem comes too quick and
makes launcher will reset the remote animation when onStop received.

Also, consolidate checks in AppTransition#goodToGo for topOpenAnim to
fix test flaky on MultiDisplayPolicyTests#testNoLeakOnExternalDisplay.

And, revert commit 5341d1c7 for modification of WC#isWaitingForTransitionStart
since it will break isAnimating(TRANSITIONS | PARENTS) usage to traverse
child activity if is waiting for transition but actually user don't add CHILDREN
flag.

Bug: 142617871
Bug: 131661052
Test: all existing tests passed

Change-Id: Ia0bb09b009c738bd27afe241ad383ddbb383a0fc