Search for label on project labels page by title or description

What does this MR do?

Adds ability to search for label on project labels page by title or description

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Its impossible to find a label on https://gitlab.com/gitlab-org/gitlab-ce/labels page as its 17 pages of them

Screenshots (if relevant)

no search

nothing found

priority and other label match

only other label match

only priority match

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/34837, https://gitlab.com/gitlab-org/gitlab-ce/issues/27031

app/controllers/projects/labels_controller.rb

@@ -151,7 +151,10 @@ def subscribable_resource
 
   def find_labels
     @available_labels ||=
-      LabelsFinder.new(current_user, project_id: @project.id, include_ancestor_groups: params[:include_ancestor_groups]).execute
+      LabelsFinder.new(current_user,
+                       project_id: @project.id,
+                       include_ancestor_groups: params[:include_ancestor_groups],
+                       search: params[:search]).execute
   end
 
   def authorize_admin_labels!