Add debugging steps for `ImagePullBackoff`
What does this MR do?
It adds debugging steps for review app failures with ImagePullBackoff on the pods. This failure is one of the most common one that typically cause widespread failures.
We have had 2 instances of this:
- introduction of single container - gitlab-org/build/CNG!387 (merged)
- fix GITLAB_EDITION for gitlab ce - !30272 (merged)
Having these steps documented would help future debugging when such failure happen again.
Edited by Yorick Peterse