Usage metrics

Some functionality the executor has is to report how much CPU/memory jobs are using.

This is turned on by changing the executor config file to include:

   exposeQueueUsageMetrics: true

The metrics are calculated by getting values from metrics-server.

When developing locally with Kind, you will also need to deploy metrics-server to allow this to work.

The simplest way to do this it to apply this to your kind cluster:

kubectl apply -f