Add settings for notification bubbling

Globally, as well as at the app and channel level

Test: atest
Bug: 123543052
Change-Id: I1668b592c5d175d77d6a38f35e7576d641175d44

src/com/android/settings/notification/AppNotificationSettings.java

@@ -152,6 +152,7 @@ public class AppNotificationSettings extends NotificationSettingsBase {
         mControllers.add(new DescriptionPreferenceController(context));
         mControllers.add(new NotificationsOffPreferenceController(context));
         mControllers.add(new DeletedChannelsPreferenceController(context, mBackend));
+        mControllers.add(new BubblePreferenceController(context, mBackend));
         return new ArrayList<>(mControllers);
     }