Insert gomplate into service containers that do not need Ruby

What does this MR do?

This MR inserts Gomplate into the following images:

• gitlab-container-registry

Future MRs will cover

• gitlab-shell
• gitaly
• gitlab-pages
• gitlab-workhorse

Related issues

Part of gitlab-org/charts/gitlab#2694 (closed)

Test

docker run --rm registry.gitlab.com/gitlab-org/build/cng/gitlab-container-registry:2694-use-gomplate gomplate -h
docker run --rm registry.gitlab.com/gitlab-org/build/cng/gitlab-container-registry:2694-use-gomplate-ubi8 gomplate -h

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
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated