Add Gitaly server-side backup to backup-utility

What does this MR do?

Add Gitaly server-side backup to backup-utility.

Related issues

gitlab-org/gitlab#438393 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated => gitlab-org/charts/gitlab!3683 (merged)
• Integration tests added to GitLab QA
• [-] The impact any change in container size has should be evaluated
• [-] New dependencies are managed with dependencies.io