Animate home in separate layer

Such that it always stays at the bottom.

Test: Open app in split-screen
Test: go/wm-smoke
Change-Id: If713c6c04e6616ff04d8475ea2da0241ed863628
Fixes: 77144130
diff --git a/services/core/java/com/android/server/wm/AppWindowToken.java b/services/core/java/com/android/server/wm/AppWindowToken.java
index 5676f58..a701d42 100644
--- a/services/core/java/com/android/server/wm/AppWindowToken.java
+++ b/services/core/java/com/android/server/wm/AppWindowToken.java
@@ -1662,7 +1662,9 @@
     }
 
     SurfaceControl getAppAnimationLayer() {
-        return getAppAnimationLayer(needsZBoost());
+        return getAppAnimationLayer(isActivityTypeHome() ? ANIMATION_LAYER_HOME
+                : needsZBoost() ? ANIMATION_LAYER_BOOSTED
+                : ANIMATION_LAYER_STANDARD);
     }
 
     @Override