Rewrote the back arrow animation

The animation now is based on physics based animations
and nicely appears and disappears. Also we're rending
it in one piece avoiding drawing artifacts.

We're now factoring in the actual position and size of the
arrow instead of just looking at its width.

Bug: 130682266
Test: observe back animations, play around with it
Change-Id: I8fc4475615d0776a082feec7400b4674ea0331a2