Resolve "Extract EE specific files/lines for spec/models/clusters"

What does this MR do?

CE counterpart in: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18866

Does this MR meet the acceptance criteria?

• Review
  • Has been reviewed by Backend
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes #5911 (closed)