Resolve "Add instrumentation classes for runners_usage metrics"

What does this MR do and why?

We are in the process of removing usage_data.rb. We do that a bit at a time by migrating chunks of metrics that are similar.

This MR migrates the 7 runners_usage metrics.

It might be easier to review this MR one commit at a time as each commit migrates a single metric.

How to set up and validate locally

If you run Gitlab::Usage::ServicePingReport.for(output: :all_metrics_values)["counts"].select{ |k,v| k.start_with? "ci_runners" } in the rails console you should get the same result on this before and after the change.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #396825 (closed)