Directly use BaseIndexableProvider

- Add function getXmlResourceId, Fragments don't need to write
xml resource id twice.
- Remove getPreferenceControllers from Indexable.java. Because it will
move to SettingsLib later for other apps which don't need this function

Bug: 135053028
Test: robolectric
Change-Id: I1e74519aecdea3dde64a5aea79f08d766dbc0003

src/com/android/settings/wfd/WifiDisplaySettings.java

@@ -835,6 +835,6 @@ public final class WifiDisplaySettings extends SettingsPreferenceFragment implem
     public static final SummaryLoader.SummaryProviderFactory SUMMARY_PROVIDER_FACTORY
             = (activity, summaryLoader) -> new SummaryProvider(activity, summaryLoader);
 
-    public static final Indexable.SearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
+    public static final BaseSearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
             new BaseSearchIndexProvider(R.xml.wifi_display_settings);
 }