Draft: Wait for GitLab to be up before printing 'GitLab available at'

What does this merge request do and why?

This MR adds a wait for GitLab to be up after running gdk start (and gdk status). If it is not up within 10 seconds, it will show a

How to set up and validate locally

1. Run gdk start
2. See 'GitLab available at' message
3. Run gdk stop
4. Run rm gitlab-http-router/wrangler.toml (restore later with gdk reconfigure)
5. Run gdk start
6. See a wait of 10 seconds
7. See the error

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.