feat(arc): add Prometheus monitoring and Grafana dashboard

[xnoto]

Summary

• expose ARC controller and listener metrics for Prometheus scraping
• add ServiceMonitor resources for the ARC system and the arc-tf runner scale set
• vendor and adapt the upstream ARC Grafana dashboard for the repo's managed Grafana instance
• update CODEOWNERS to assign the repo to @makeitworkcloud/admins

Details

This adds ARC monitoring that fits the cluster's existing kube-prometheus-stack and Grafana setup.

ARC controller metrics are enabled on the controller chart, and listener metrics are enabled on the arc-tf scale set. The new monitoring resources expose and scrape:

• the ARC controller in arc-systems
• the arc-tf listener in arc-runners

The Grafana side now includes an adapted version of ARC's upstream autoscaling runner set dashboard, wired to the cluster's default Prometheus datasource. The dashboard was patched to remove upstream sample-specific hardcoded scale set names and namespaces so it works with this repo's arc-tf configuration.

This PR also keeps minRunners: 1 for arc-tf, as intended.

Validation

• ran pre-commit run --files .github/CODEOWNERS operators/arc/arcsystem.yaml workloads/arc/arc-tf-application.yaml workloads/arc/kustomization.yaml workloads/arc/metrics-monitoring.yaml workloads/grafana/datasource.yaml workloads/grafana/arc-dashboard.yaml workloads/grafana/kustomization.yaml
• all checks passed

Notes

• runner pods themselves do not expose separate ARC-specific metrics; ARC's meaningful metrics surfaces are the controller-manager and scale-set listeners
• full local kustomize build for workloads/arc was not verified in this environment because ksops generator plugins are disabled here