Draft: Allow GDK to be used for QA tests

What does this Merge Request do and why?

Extends GDK's Dockerfile to allow QA tests to be run against it.

See https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/1011

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.