Implement querySiteMapPairs for indexableProvider.

Query sitemap will return a list of pairs [parent class name, child
class name]. It's up to consumer to figure out the display name later
so the provider doesn't have dependency on localizing any display names.

- Removed SiteMapManagerTest. We will perform the test in
  SettingsIntelligence instead.
- Added test for the new provider in instrumentation test (robolectric
  doesn't recognize the new constants in framework yet)

Bug: 67359411
Bug: 64938328
Test: atest
Change-Id: Ia973115320e6b7c8cf84d4756db1763ae7010aed