Add a helper to create, cache and execute queries.
Move some test-only methods into head_interests and update with the new query style.
Add a helper to convert date to days in preparation to store days instead of dates for visits.
Add a helper to extract the namespace from a full interest name.
Combine metadata table into the main interests table and expose setInterest/getInterests to access it.
Update moz_up_interests_hosts to moz_interests_hosts and implement new addInterestHost from addInterestForHost.
Update moz_up_interests_visits to moz_interests_visits with days and visits instead of date_added and visit_count and change statements to use that new structure.
Convert clearRecentInterests to clearRecentVisits with the new query style.
Convert getBucketsForInterest to getBucketsForInterests with the new query style.
Rework the service's getTopInterests to chain multiple promises together now that diversity and buckets accept an array of interests. Remove the service's wrapper for getBucketsForInterests and update callers to directly call storage.
Convert reprocessRecentHistoryVisits to getRecentHistory with the new query style.
Convert getTopInterests to getScoresForNamespace with the new query style.
Allow for zero-scores so that the API always returns the right number of interests.
Update getDiversityForInterests to use the new query style.
Clean up various unused code in PlacesInterestsStorage.