copy AnimatorSet and related classes from AOSP

This makes AnimatedVectorDrawableCompat from androidx functional and
probably also helps other animation stuff.

src/api-impl/android/view/ViewAnimationUtils.java

@@ -1,10 +1,11 @@
 package android.view;
 
 import android.animation.Animator;
+import android.animation.ValueAnimator;
 
 public class ViewAnimationUtils {
 
 	public static Animator createCircularReveal(View view, int centerX, int centerY, float startRadius, float endRadius) {
-		return new Animator();
+		return new ValueAnimator();
 	}
 }