Misc tweaks to Indexable usage and tests.

- Make SettingsPreferenceFragment implement Indexable directly
- Add existing fragments that are SettingsPrefFragment but not Indexable
  to grandfather list.
- Fix "font size" fragment so it shows up in search properly.
- Remove duplicates for "lock screen display", "Screen saver".

Bug: 70720645
Test: robotests
Change-Id: I44ce0cac0fdf5e882b315861bb4bebc45dbe01e6

src/com/android/settings/PreviewSeekBarPreferenceFragment.java

@@ -97,9 +97,9 @@ public abstract class PreviewSeekBarPreferenceFragment extends SettingsPreferenc
 
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
-                             Bundle savedInstanceState) {
+            Bundle savedInstanceState) {
         final View root = super.onCreateView(inflater, container, savedInstanceState);
-        final ViewGroup listContainer = (ViewGroup) root.findViewById(android.R.id.list_container);
+        final ViewGroup listContainer = root.findViewById(android.R.id.list_container);
         listContainer.removeAllViews();
 
         final View content = inflater.inflate(mActivityLayoutResId, listContainer, false);