Move bubble settings to their own page

To make room for graphics/longer descriptive text

Test: robotests
Bug: 129068779
Change-Id: Iac6ea43bd3a0cddc487ff3d1bbd8f35142294d01

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

@@ -56,7 +56,7 @@ public class BubbleNotificationPreferenceController extends TogglePreferenceCont
     @Override
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);
-        Preference preference = screen.findPreference(NOTIFICATION_BUBBLES);
+        Preference preference = screen.findPreference(getPreferenceKey());
         if (preference != null) {
             mSettingObserver = new SettingObserver(preference);
         }