Polish reveal animation after onTasksAppeared.

Showing the animation leash of appearedTaskTargets if there need to
play the reveal animation behind splash screen view.
Pausing applyDepthAndBlur while playing splash screen exit animation
from launcher side, otherwise the app window would be blurred.

Bug: 277704255
Test: manual, do quickswitch to start the app behind splash screen
view, verify no flicker or blur happen when playing reveal animation.

Change-Id: I83604ceeaeb54ab2100fdabf45a1624644b85e37