Implement etcd backup and restore

• CKA 1.24, CKA 1.23, CKA 1.20

• Ref: https://kubernetes.io/docs/tasks/administer-cluster/configure-upgrade-etcd/#backing-up-an-etcd-cluster

• etcdctl snapshot save

See also

• etcd, etcdctl, etcdctl snapshot save, etcd versions, etcdHighNumberOfFailedGRPCRequests
• CKA: v1.28: API, Namespace, Pods, secrets, Services, deployments, nodes, Volumes, Ingress, CKS