Draft: Update last tier pipeline status if it's last tier

What does this MR do and why?

Update last tier pipeline status if it's last tier

How to set up and validate locally

TODO

• Create the status check at: https://gitlab.com/gitlab-org/gitlab/-/settings/merge_requests
  • Do not tick Status checks must succeed. We'll do that after everything is set up
  • We need to decide what to fill in API to check so that it's not:
    • It should not be confusing. It should be indicated that we're not really using that URL
    • It should be considered secure and safe to hammer the specific URL
• Fill VERIFY_LAST_TIER_PIPELINE_STATUS_ID in the CI/CD variables (the id from the above status check we created) at: https://gitlab.com/gitlab-org/gitlab/-/settings/ci_cd

Related to #462819 (closed)