Allow AOSP SettingsIntelligence to have visibility of apps

Follow the Declaring package visibility needs.

- SettingsIntelligence queries SearchIndexablesProviders to show
  Search results in Settings. It currently has visibility of apps
  for intent action android.intent.action.MAIN.
- Add visibility for apps with intent signature
  SEARCH_INDEXABLES_PROVIDER.

Fixes: 236813510
Test: manuall test and obersve the index database
Change-Id: I62f5d1a647427e61b74639ca6295f0a6530f643f