Adds a special one-off tag for GitLab-Shell

What does this MR do?

• This fixes an issue where preprod is unable to utilize an appropriate version of GitLab-Shell due to tagging discripencies
• We add a special tag to GitLab-Shell gitlab-<GITLAB_VERSION>
• Logic is included in the deployment helm template for preprod to detect when it should use this one-off tag

This work is in tandem with: gitlab-com/gl-infra/k8s-workloads/gitlab-com!720 (merged)

Related issues

Addresses: gitlab-com/gl-infra/delivery#1565 (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

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes n/a
• Documentation created/updated - This is specific to Delivery's needs for GitLab.com release procedures
• Integration tests added to GitLab QA - n/a
• The impact any change in container size has should be evaluated - n/a