Improve the loading time of DataSaverSummary

Use AppListRepository instead of ApplicationsState can achieve better
performance.

Fix: 280280596
Test: Manually on Data Saver page
Test: Unit test
Change-Id: I98cbae50500b90e7e7f6101fb064003339b082c1

src/com/android/settings/datausage/DataSaverBackend.java

@@ -196,8 +196,10 @@ public class DataSaverBackend {
     public interface Listener {
         void onDataSaverChanged(boolean isDataSaving);
 
-        void onAllowlistStatusChanged(int uid, boolean isAllowlisted);
+        /** This is called when allow list status is changed. */
+        default void onAllowlistStatusChanged(int uid, boolean isAllowlisted) {}
 
-        void onDenylistStatusChanged(int uid, boolean isDenylisted);
+        /** This is called when deny list status is changed. */
+        default void onDenylistStatusChanged(int uid, boolean isDenylisted) {}
     }
 }