SysUI: Status bar ImageViews

- Switch AlphaOptimizedImageView to have the boolean hasOverLappingRendering()
  return be a custom value. This allows us to have AnimatedImageView extend
  AlphaOptimizedImageView and support both types of ImageViews w/o having to
  create 2x subclasses.
- Add drawable ID tracking to AnimatedImageView so that we don't interrupt
  animations with an update of the exact same drawable.
- Switch mobile signal icon to use AnimatedImageView so that animations aren't
  interrupted.

Bug: 21504588
Change-Id: Ic2275f1bf607449c191ae0d08bc7756c7d694bc1