kube-prometheus: Make grafana dashboards non-editable

assets/grafana/_grafanalib.py

assets/grafana/kubernetes-capacity-planning.dashboard.py

assets/grafana/kubernetes-cluster-health.dashboard.py

assets/grafana/kubernetes-control-plane-status.dashboard.py

assets/grafana/kubernetes-resource-requests.dashboard.py

assets/grafana/nodes.dashboard.py

assets/grafana/pods.dashboard.py

assets/grafana/raw-json-dashboards/etcd-dashboard.json

manifests/grafana/grafana-dashboards.yaml