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/ChannelNotificationSettings.java

@@ -115,7 +115,7 @@ public class ChannelNotificationSettings extends NotificationSettingsBase {
         mControllers.add(new DndPreferenceController(context, mBackend));
         mControllers.add(new NotificationsOffPreferenceController(context));
         mControllers.add(new BubblePreferenceController(context, getChildFragmentManager(),
-                mBackend));
+                mBackend, false /* isAppPage */));
         return new ArrayList<>(mControllers);
     }
 }