Fix SurfaceAnimator and SurfaceAnimationRunner tests

Since we marked mAnimator.mInitialized to true in the tests,
WM executed things from another thread during tests leading to
concurrency bugs.

Instead, we stub out addAfterPrepareSurfacesRunnable to a consumer
which executes the runnable directly during tests, avoiding the
need to let WM process animation frames.

Also attempts to fix flakyness in SurfaceAnimationRunner

Test: go/wm-smoke
Test: SurfaceAnimatorTest
Test: SurfaceAnimationRunnerTest

Change-Id: Ic9522e1afef6ce62667aefca80e58d6fb1db3424
Fixes: 71650763
Fixes: 71602314
Bug: 71719744