[RFE] Worker platform resource usage

[josecastillolema]

Is your feature request related to a problem? Please describe.
Today we collect the worker's average and maximum memory and CPU usage (https://github.com/kube-burner/kube-burner-ocp/blob/main/cmd/config/metrics-report.yml#L283-L297). This (and please correct me if I am wrong) includes the CPU/memory of the kube-burner workload itself.

Describe the solution you'd like
I would like to add new metrics (average and maximum for memory and CPU) for platform usage. This means the resource consumption observed from the OS + platform (OCP) without user workloads. Only for workers.

Additional context
Some PMs have requested this as they argue that the resources consumed from the kubeburner itself are not of interest to the user.
On top of that, makes it harder to compare the behavior of the platform between different workloads.

[josecastillolema]

cc @Noreen21 @wilsondav