Update the Settings database to enable Payloads

Add Payload and Payload type columns to the settings
database. This includes extending preference controllers
to map their settings to UI components so that the
payload results can be consumed by a front end.

Change-Id: I889dcc4ff7793306718d12e1e5993386b58f21cc
Fixes: 33451851, 33390556
Test: RunSettingsRoboTests

src/com/android/settings/search/BaseSearchIndexProvider.java

@@ -18,6 +18,7 @@ package com.android.settings.search;
 
 import android.content.Context;
 import android.provider.SearchIndexableResource;
+import com.android.settings.core.PreferenceController;
 
 import java.util.Collections;
 import java.util.List;
@@ -46,4 +47,9 @@ public class BaseSearchIndexProvider implements Indexable.SearchIndexProvider {
     public List<String> getNonIndexableKeys(Context context) {
         return EMPTY_LIST;
     }
+
+    @Override
+    public List<PreferenceController> getPreferenceControllers(Context context) {
+        return null;
+    }
 }