Add RestateCluster compute spec imagePullSecrets property

[pcholakov]

Am I holding this right?

~/restate/operator % kg rsc/restate-test -o yaml
apiVersion: restate.dev/v1
kind: RestateCluster
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"restate.dev/v1","kind":"RestateCluster","metadata":{"annotations":{},"name":"restate-test"},"spec":{"compute":{"image":"ghcr.io/restatedev/restate@sha256:ebdcb2d4e031d316f5adbeccce3c0fecad510813d06c39d4612a63b66d98fde9","imagePullSecrets":[{"name":"ghcr-secret"}]},"storage":{"storageRequestBytes":2147483648}}}
  creationTimestamp: "2025-07-29T13:31:29Z"
  finalizers:
  - clusters.restate.dev
  generation: 10
  name: restate-test
  resourceVersion: "83819"
  uid: de515dbf-d9b6-4375-8707-8ef5dd80b4e7
spec:
  compute:
    image: ghcr.io/restatedev/restate@sha256:ebdcb2d4e031d316f5adbeccce3c0fecad510813d06c39d4612a63b66d98fde9
    imagePullSecrets:
    - name: ghcr-secret
  storage:
    storageRequestBytes: 2147483648
status:
  conditions:
  - lastTransitionTime: "2025-07-29T13:54:51Z"
    message: Restate Cluster provisioned successfully
    reason: Provisioned
    status: "True"
    type: Ready

~/restate/operator % kg po restate-0 -o yaml | grep imagePullSecrets -C 3
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"restate.dev/v1","kind":"RestateCluster","metadata":{"annotations":{},"name":"restate-test"},"spec":{"compute":{"image":"ghcr.io/restatedev/restate@sha256:ebdcb2d4e031d316f5adbeccce3c0fecad510813d06c39d4612a63b66d98fde9","imagePullSecrets":[{"name":"ghcr-secret"}]},"storage":{"storageRequestBytes":2147483648}}}
  creationTimestamp: "2025-07-29T13:54:50Z"
  generateName: restate-
  labels:
--
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  hostname: restate-0
  imagePullSecrets:
  - name: ghcr-secret
  nodeName: orbstack
  preemptionPolicy: PreemptLowerPriority