Move static search ranking from DatabaseResultLoader to Search Adapter.

This will avoid unnecessary static ranking if smart ranking is used.

Since loader does not need to provided sorted collection of results,
the loading data type has changed from List<> to Set<>. This will also
faster lookup in the Adapter.

Fixes: 38447799
Test: make RunSettingsRoboTests

Change-Id: I448b29bd4e8700c8ec4b5766cbeab4b3087ae39a