Revert "Shift RoundedCornerOverlay to Display window hierarchy"

This reverts commit b212cbaca3.

Reason for revert: DPU SysMMU Page Fault

Bug: b/231553814

Change-Id: Ida1aed955c0d02461bc0cb55278a05489cd6b068

services/core/java/com/android/server/wm/WindowToken.java

@@ -378,7 +378,7 @@ class WindowToken extends WindowContainer<WindowState> {
     SurfaceControl.Builder makeSurface() {
         final SurfaceControl.Builder builder = super.makeSurface();
         if (mRoundedCornerOverlay) {
-            builder.setParent(getDisplayContent().getSurfaceControl());
+            builder.setParent(null);
         }
         return builder;
     }