WIP: Move EE specific code out of app/services

What does this MR do?

This moves all remaining EE specific code out of app/services and into ee/app/services/ee.

CE backport MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25165

TODO

• app/services/search/project_service.rb
• app/services/search/group_service.rb
• app/services/issuable/clone/base_service.rb
• app/services/system_hooks_service.rb
• app/services/notes/quick_actions_service.rb
• app/services/git_tag_push_service.rb
• app/services/concerns/exclusive_lease_guard.rb
• app/services/create_branch_service.rb
• app/services/protected_branches/legacy_api_update_service.rb
• app/services/protected_branches/api_service.rb
• app/services/git_push_service.rb
• app/services/notification_recipient_service.rb

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/8602

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• EE specific content should be in the top level /ee folder
• Security reports checked/validated by reviewer