Index Nightdisplay Settings into search

Adds a SearchIndexProvider into NightDisplaySettings
to index night_display_settings.xml. It will show
up in search as long as ColorDisplayController
is available.

Also, supress the search result for Night Display
under Display settings in favor of the actual toggle.

Test: robotests
Fixes: 69852201

Change-Id: Id014a5ab03e7a6b5fc99f79a1cb41a0c06323f9c

src/com/android/settings/DisplaySettings.java

@@ -56,6 +56,8 @@ public class DisplaySettings extends DashboardFragment {
     private static final String KEY_SCREEN_TIMEOUT = "screen_timeout";
     private static final String KEY_AMBIENT_DISPLAY = "ambient_display";
 
+    private static final String KEY_NIGHT_DISPLAY = "night_display";
+
     @Override
     public int getMetricsCategory() {
         return MetricsEvent.DISPLAY;
@@ -126,6 +128,7 @@ public class DisplaySettings extends DashboardFragment {
                     keys.add(KEY_DISPLAY_SIZE);
                     keys.add(WallpaperPreferenceController.KEY_WALLPAPER);
                     keys.add(KEY_AMBIENT_DISPLAY);
+                    keys.add(KEY_NIGHT_DISPLAY);
                     return keys;
                 }