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/connecteddevice/AdvancedConnectedDeviceDashboardFragment.java

@@ -108,9 +108,6 @@ public class AdvancedConnectedDeviceDashboardFragment extends DashboardFragment
                         keys.add(AndroidBeamPreferenceController.KEY_ANDROID_BEAM_SETTINGS);
                     }
 
-                    // Parent duplicate
-                    keys.add(KEY_BLUETOOTH);
-
                     return keys;
                 }