Enable skopeo for container releases

Enable skopeo for container releases

- Adds option that enables container copies with skopeo
  instead of pull the image, re-tag, and then push it
- Retains current pull/re-tag/push behavior as default

Related https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/5673

Signed-off-by: Balasankar 'Balu' C <balasankar@gitlab.com>

What does this MR do?

Move away from the pull-retag-push logic for releasing Docker images towards skopeo copy. This will help when we finally do multiarch images.

Testing

Unfortunately, this is kinda impossible to test in live without setting up a lot of infrastructure. Hence, I added an env variable flag to control this, so we can test this in nightlies. The default flow still remains the same.

Related issues

#5673

Checklist

See Definition of done.

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

Required

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Expected (please provide an explanation if not completing)

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