[Unfold animation] Move the dark scrim below

How rotation animation works:
* It captures a screenshot of the screen
* It puts the screenshot over everything on the
  screen (in a container with z-index
  Integer.MAX_VALUE)
* Starts the process of resizing windows to the
  new size. Because the screenshot on top of
  everything, the resizing is not visible.

Black unfold overlay is also added with
z-index Integer.MAX_VALUE but because it is
added later it is rendered on top of the
rotation screenshot. So it is visible how
the overlay is resized.

Updated z-index of the unfold overlay to render
below the rotation animation screenshot to hide
it while we are rotating.

Bug: 258213952
Bug: 255955520
Test: manual fold and going to tabletop mode after rotating
  (see comparison videos in the CL)
Change-Id: I5e9b5c72dfa28e4ae9f447ad8df7b403c97bf43e

packages/SystemUI/src/com/android/systemui/unfold/UnfoldLightRevealOverlayAnimation.kt

@@ -94,7 +94,7 @@ constructor(
                 overlayContainer = builder.build()
 
                 SurfaceControl.Transaction()
-                    .setLayer(overlayContainer, Integer.MAX_VALUE)
+                    .setLayer(overlayContainer, UNFOLD_OVERLAY_LAYER_Z_INDEX)
                     .show(overlayContainer)
                     .apply()
 
@@ -268,4 +268,12 @@ constructor(
                 this.isFolded = isFolded
             }
         )
+
+    private companion object {
+        private const val ROTATION_ANIMATION_OVERLAY_Z_INDEX = Integer.MAX_VALUE
+
+        // Put the unfold overlay below the rotation animation screenshot to hide the moment
+        // when it is rotated but the rotation of the other windows hasn't happen yet
+        private const val UNFOLD_OVERLAY_LAYER_Z_INDEX = ROTATION_ANIMATION_OVERLAY_Z_INDEX - 1
+    }
 }