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/gestures/GestureSettings.java

@@ -75,12 +75,5 @@ public class GestureSettings extends DashboardFragment {
                     sir.xmlResId = R.xml.gestures;
                     return Arrays.asList(sir);
                 }
-
-                @Override
-                protected boolean isPageSearchEnabled(Context context) {
-                    // All rows in this screen can lead to a different page, so suppress everything
-                    // from this page to remove duplicates.
-                    return false;
-                }
             };
 }