Remove scope permissions check from search service

Background

Follow up from !155516 (merged) and !158213 (closed)

Adding a new scope to SearchService requires adding support in SearchNavigation class. Even if the scope is just being added to the service and not the search UI.

This is due to checking whether the user has permissions in the specific project to do a search for that scope. See Search::ProjectService. The scope will be changed to a default scope if not allowed.

Proposal

Scope permissions check should be done higher up in the code and removed from the service. Move the check to SearchController and the API::Search to return an error early if the user attempts to run a search for a scope they do not have permissions for.