Suggest enabling telemetry for team members

What does this merge request do and why?

This MR adds a doctor diagnostic to suggest team members to enable telemetry if they haven’t.

A community contributor will never see this, unless they set their user.email Git setting to an @gitlab.com address.

How to set up and validate locally

1. Disable telemetry if you have it enabled (gdk config set telemetry.enabled false)
2. Run gdk doctor
3. See the suggestion
   

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.