Settings search - Navigate user to exact page

- remove duplicate index preference
- default set searchable = false when the preference has fragment
- make some fragments indexable

Bug: 143057584
Test: robotest & manual

Change-Id: I4d64f6106d2f92f0a45e8c7e26388677f593f412

src/com/android/settings/applications/assist/ManageAssist.java

@@ -37,7 +37,6 @@ import java.util.List;
 public class ManageAssist extends DashboardFragment {
 
     private static final String TAG = "ManageAssist";
-    private static final String KEY_ASSIST = "gesture_assist_application";
 
     @Override
     protected String getLogTag() {
@@ -85,12 +84,5 @@ public class ManageAssist extends DashboardFragment {
                         Context context) {
                     return buildPreferenceControllers(context, null /* lifecycle */);
                 }
-
-                @Override
-                public List<String> getNonIndexableKeys(Context context) {
-                    List<String> keys = super.getNonIndexableKeys(context);
-                    keys.add(KEY_ASSIST);
-                    return keys;
-                }
             };
 }