Fix fraction, and other cleanup

Fraction is now from animation start to end state. This makes it
more in line with other animation fraction meaning. Also, the app
can figure out the animation direction on its own by inspecting
the visibility state when the animation gets prepared.

Also fix some other stuff in WindowInsetsAnimationCallback.

Test: CTS coming soon
Bug: 118118435
Change-Id: I81d36159817719a9b0ee25bb78cfbfddc2029270