prev/next cache should not do double-ended wildcard search

The civicrm_prev_next_cache is searched using the following condition:
WHERE cacheKey LIKE '%civicrm search 8d293ba30d24366769b0d6d62285aafe_2168%

If there is a prefix added to the key, that should be refactored into a separate key "domain" or whatever the prefix contains, so that we only need the wildcard at the end.