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/display/ScreenZoomSettings.java

@@ -27,7 +27,6 @@ import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
 import com.android.settings.PreviewSeekBarPreferenceFragment;
 import com.android.settings.R;
 import com.android.settings.search.BaseSearchIndexProvider;
-import com.android.settings.search.Indexable;
 import com.android.settings.search.SearchIndexableRaw;
 import com.android.settingslib.display.DisplayDensityUtils;
 import com.android.settingslib.search.SearchIndexable;
@@ -39,7 +38,7 @@ import java.util.List;
  * Preference fragment used to control screen zoom.
  */
 @SearchIndexable(forTarget = SearchIndexable.ALL & ~SearchIndexable.ARC)
-public class ScreenZoomSettings extends PreviewSeekBarPreferenceFragment implements Indexable {
+public class ScreenZoomSettings extends PreviewSeekBarPreferenceFragment {
 
     private int mDefaultDensity;
     private int[] mValues;