DisplayCutout: Add emulation option to DeveloperSettings

Bug: 65689439
Test: Go to Developer Settings > Toggle "Emulate display with a cutout"
Change-Id: Id3387c026df9868d42e0a7b0d7e623115f41452b

tests/robotests/src/android/content/om/IOverlayManager.java

@@ -16,7 +16,11 @@ package android.content.om;
 
 import android.os.IBinder;
 
-public class IOverlayManager {
+public interface IOverlayManager {
+
+    public OverlayInfo getOverlayInfo(String packageName, int userId);
+
+    public boolean setEnabled(java.lang.String packageName, boolean enable, int userId);
 
     public static class Stub {
         public static IOverlayManager asInterface(IBinder b) {

tests/robotests/src/android/content/om/OverlayInfo.java

@@ -15,4 +15,9 @@
 package android.content.om;
 
 public class OverlayInfo {
-}
+
+    public boolean isEnabled() {
+        return false;
+    }
+
+}