Add an activity for testing WindowInsetsController

Which tests these APIs:
- WindowInsetsController#setSystemBarsBehavior
- WindowInsetsController#show
- WindowInsetsController#hide
- WindowInsetsController#addOnControllableInsetsChangedListener
- WindowInsetsController#controlWindowInsetsAnimation
- WindowInsetsAnimationController#setInsetsAndAlpha
- WindowInsetsAnimationController#finish

Bug: 118118435
Test: Manual test
Change-Id: I7f365007abf2c3e6f04e1493e8be7aaef07cb807