Optimize queries in "/projects/:id/share_locations" API endpoint

The following discussion from !113329 (merged) should be addressed:

• @manojmj started a discussion: (+3 comments)

  Context: This search method runs the default parameter of include_parents: false, which does not search for full paths.

  What we can just use instead is the by_search method from base.rb, which already runs with include_parents: true, so searching by full path will just work as intended, which we already use in finders in the same hierarchy, like in this finder.