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/Indexable.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.List;
 
@@ -65,5 +66,11 @@ public interface Indexable {
          * @return a list of {@link SearchIndexableRaw} references. Can be null.
          */
         List<String> getNonIndexableKeys(Context context);
+
+        /**
+         * @param context
+         * @return a list of {@link PreferenceController} for ResultPayload data during Indexing.
+         */
+        List<PreferenceController> getPreferenceControllers(Context context);
     }
 }