Add summary of outdated runners to the Group view for managing runners

Release notes

Suppose you manage a large fleet of runners at the group level, either on GitLab.com or self-managed. In that case, it is more time-consuming and challenging to identify which runners associated with the group namespace are outdated. Failing to update runner versions doesn't just mean you aren't using the latest features - it could also mean that you aren't taking advantage of security fixes. The Group > Runners view now includes two status badges for outdated Runner versions. The first shows a count of outdated runners recommended for an upgrade, and the second is the count of outdated runners where an upgrade is available. The view now also includes the upgrade status badge that displays either upgrade recommended or upgrade available next to a runner that needs an update. Finally, there is a filter option to easily filter the view to display only the list of runners that needs a version update.

Overview

In #365078 (closed) we are adding the outdated runners metric to the Admin Area > Runners view. The next iteration is to add this feature to the Groups view for managing runners.