Add new HTTP Router service

What does this merge request do and why?

Related issue: gitlab#450958 (closed)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Check out this branch gitlab_http_router_service
2. Stop your GDK
3. Run gdk config set gitlab_http_router.enabled true
4. Set up a local interface
5. Run make Procfile gitlab-http-router-setup. It should install the repo, and run npm install.
6. You can also run make gitlab-http-router-update as well to ensure this works
7. Now run gdk start. A new service gitlab-http-router should now start.
8. You can monitor with gdk tail gitlab-http-router
9. Go to http://gdk.test:9393. This should work just like gdk.test:3000 but is proxied via the HTTP router.

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.