Bubble settings: feature, notification, app

* Removed setting from developer options
* Removed bubble settings from normal notifications /
  channels

* Feature available via notification setting
* Feature screen with educational gif

* App level is now a tri-state choice of all / selected /
  none
* App level bubble controls are accessible top-level in
  app notifications

Test: make -j40 RunSettingsRoboTests ROBOTEST_FILTER="Bubble"
Bug: 138116133
Change-Id: Id103e9d3717fdc9b86a916be40c43cda9c35ac34

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

@@ -30,6 +30,9 @@ import com.android.settingslib.search.SearchIndexable;
 import java.util.ArrayList;
 import java.util.List;
 
+/**
+ * App level settings for bubbles.
+ */
 @SearchIndexable
 public class AppBubbleNotificationSettings extends NotificationSettings implements
         GlobalBubblePermissionObserverMixin.Listener {