Improve Admin runners list view empty state when there are no registered runners
Details
When prepping for the UX Scorecard evaluation, I found the design of the empty runners list was not providing me with information on how to use the feature. We include the top card above the list view, but that really is the main action when there are no runners registered. This is also documented in the UX Scorecard recommendations.
Solution proposal
Improve the empty state when there are no runners registered to consolidate space, be more consistent with other areas, and give the user an action to fix the current state. This should be based on https://design.gitlab.com/regions/empty-states and also on what comes out of gitlab-org/gitlab-services/design.gitlab.com#1053 (closed).