Set default, workflow, and use rules in CI config

What does this Merge Request do?

This adds:

• Sane defaults, including the gitlab-org tag so that Community contribution pipelines run on GitLab's runners
• Sane workflow:rules
• Support for rules
• The gitlab-org-docker tag for jobs that needs DinD (same reason as for the gitlab-org tag above)

This is part of gitlab#212970 (closed).

Merge Request checklist

• Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.