Make WC#applyAnimation can apply on Task / TaskStack layer (2/N)

- Introduce WC#getAnimatingContainer to get the current animating container:
  When Task / TaskStack level animation enabled, some checks  in WallpaperController,
  like to check wallpaper.mActivityRecord.getAnimation.getShowWallpaper if the animation
  should show wallpaper, would need to use this method to get the value from
  the upper layer of animating container.

- Fix some places that calls isAnimating() needs to add PARENTS flag in
  WallpaperController / WindowState

Bug: 142617871
Bug: 131661052
Test: atest WindowContainerTests, WallpaperControllerTests

Change-Id: I842f377d643d43104facaba4f401a76ef9dd2ce0