Add gdk.yml generator for use in Remote Dev workspace

What does this merge request do and why?

This is the first iteration of a support script which can be used in the context of a remote development workspace.

In this case, it assumes there are some variables being set in the environment:

• GL_WORKSPACE_DOMAIN_TEMPLATE=${PORT}-workspace-62637-2083197-l4n51w.workspace.domain.name - This is injected by GitLab
• WORKSPACE_62637_2083197_L4N51W_SERVICE_PORT_GDK_3000=3000 - This is set by Kubernetes based on the devfile including an endpoint called GDK:

      endpoints:
        - name: gdk-3000
          targetPort: 3000

Related to gitlab-org/developer-relations/contributor-success/team-task#254 (closed)

How to set up and validate locally

1. Set up a Remote Development Workspace (follow the issue above if you need)
2. Use a devfile like this (in a GDK project/fork): https://gitlab.com/srza/gdk-rdev/-/blob/main/.devfile.yaml (This devfile uses a 'bootstrapped' GDK container)
3. Once the workspace is up, run support/gitlab-remote-dev/remote-dev-gdk-bootstrap.sh - it should add a gdk.yml file.
4. Install GDK gdk install and wait
5. GDK should start up successfully

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

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 an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.