Add add/remove for AnimationListener's

FragmentManagerImpl in AndroidX currently uses reflection to read
mListener, so it can wrap it with another listener. Adding add/remove
methods for AnimationListener's next to setAnimationListener removes the
need for AndroidX to touch mListener, which is private API.

Bug: 117519981
Test: atest AnimationTest
Change-Id: I69cb19d61078215ca6697b3d41f4c536decc2e6e