Add shared runner stats
Statistics on the public shared CI runner(s) should be added to the status page. This would help GitLab.com users to determine if there are any current issues with the CI runners or just a large backlog.
Specific stats that might be useful include:
- Number of DigitalOcean runner instances (to determine if there is any spare capacity in the runners)
- Total age of runner instances (to determine if the CI jobs being run are taking a while)
- Number of runner instances started in the past X minutes (to determine if new jobs are starting)
These statistics are not suitable for GitLab CE/EE itself, as this information is an implementation detail in the GitLab CI runner. In GitLab CE/EE, additional statistics, such as the size of the backlog, would be useful as well.
/cc @jnijhof @connorshea @sytses @ayufan
Related: gitlab-org/gitlab-ce#18178