App Bubble control page should always be available, even if off globally

There is API to open up the app-specific bubble page, therefor, we should
always show the toggle. The previous work to move bubbles to developer
settings broke this.

This CL adds a param to the controller to note whether it's the app
specific page or not (since controller is also used for channel settings)
to enable this behaviour.

Added a test for this situation.

Test: make -j40 RunSettingsRoboTests ROBOTEST_FILTER=Bubble
Bug: 131846917
Change-Id: I72b1f4b5b033d1b24281061cfa6bed4d734dfcb1

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

@@ -64,7 +64,7 @@ public class AppBubbleNotificationSettings extends NotificationSettingsBase impl
         controllers.add(new BubblePreferenceController(context, fragment != null
                 ? fragment.getChildFragmentManager()
                 : null,
-                new NotificationBackend()));
+                new NotificationBackend(), true /* isAppPage */));
         return controllers;
     }