[Experiment] Create a prototype for the new pull mirroring implementation
Part of the epic: https://gitlab.com/groups/gitlab-org/-/epics/8685
* Issue description: https://gitlab.com/gitlab-org/gitlab/-/issues/12758
* Thread: https://gitlab.com/gitlab-org/gitlab/-/issues/12758#note_1076704861
## Goal
* Verify the proposed design and test a prototype
* If successful, create follow-up issues
issue