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