[slice] Use patch in admissioncheck controller

[j-skiba]

Description

Purpose of the admissioncheck controller is to let know Kueue that slice controller is functional. In the meantime Kueue adds a finalizer which may result in a conflict error and excessive logs.

admissioncheck managedFields:

 managedFields:
  - apiVersion: kueue.x-k8s.io/v1beta1
    fieldsType: FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .: {}
          f:kubectl.kubernetes.io/last-applied-configuration: {}
      f:spec:
        .: {}
        f:controllerName: {}
        f:retryDelayMinutes: {}
    manager: kubectl-client-side-apply
    operation: Update
    time: "2026-01-15T07:30:58Z"
  - apiVersion: kueue.x-k8s.io/v1beta1
    fieldsType: FieldsV1
    fieldsV1:
      f:metadata:
        f:finalizers:
          .: {}
          v:"kueue.x-k8s.io/resource-in-use": {}
    manager: kueue
    operation: Update
    time: "2026-01-15T07:30:58Z"
  - apiVersion: kueue.x-k8s.io/v1beta1
    fieldsType: FieldsV1
    fieldsV1:
      f:status:
        .: {}
        f:conditions:
          .: {}
          k:{"type":"Active"}:
            .: {}
            f:lastTransitionTime: {}
            f:message: {}
            f:observedGeneration: {}
            f:reason: {}
            f:status: {}
            f:type: {}
    manager: manager
    operation: Update
    subresource: status
    time: "2026-01-15T07:30:58Z"
  name: slice-ac
  resourceVersion: "1131"
  uid: 58d426c4-4209-4b91-b525-9dc0b14141e7

Issue

---

Testing

manual testing

[PBundyra]

Can we use SSA as in #966