Use searchable="false" to suppress nonIndexables.

When possible, remove or simplify getNonIndexable() logic in fragments,
and use searchable="false" in xml to suppress index.

Change-Id: I5bdf5bc7d5494a64cdd9e230a51321a4b210af69
Fixes: 112608186
Test: robotest and manual search

src/com/android/settings/fuelgauge/BatterySaverController.java

@@ -49,7 +49,7 @@ public class BatterySaverController extends BasePreferenceController
 
     @Override
     public int getAvailabilityStatus() {
-        return AVAILABLE;
+        return AVAILABLE_UNSEARCHABLE;
     }
 
     @Override