addition of cluster get and sync status

[scott-cotton]

depends on signadot/go-sdk#35

Example:

23-10-25 scott@air cli % ./signadot cluster get minikube -o yaml
createdAt: 2023-09-14T22:55:21Z
name: minikube
operator:
  version: 0.14.0
syncStatus:
  lastError: "can't get cluster: invalid connection"
  lastErrorTime: 2023-10-25T01:44:33+02:00
  lastSync:
    routegroups:
      clusterState: []
      errors: []
    sandboxes:
      clusterState:
      - count: 2
        readyCondition: "true"
        readyReason: AllDesiredWorkloadsReady
      errors: []
    time: 2023-10-25T15:21:20+02:00
23-10-25 scott@air cli % ./signadot cluster get minikube
NAME       CREATED                OPERATOR VERSION   LAST SYNC
minikube   2023-09-14T22:55:21Z   0.14.0             2023-10-25T15:21:50+02:00

Please note there is some known issues w.r.t. omit empty and go-sdk: https://github.com/signadot/signadot/issues/2226