WIP: Resolve ".gitlab-setup should use an env variable to specify the repo URL for gitlab-test"

What does this MR do?

This makes jobs that download/clone a repo from GitLab.com able to download it from dev.gitlab.org instead.

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

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] API support added
• [-] Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a Backend maintainer
• Conform by the merge request performance guides
• Conform by the style 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?

Closes #32493 (moved), #32492 (moved).