Support `namespaceObject` in MAP

[utam0k]

MAP provides access to the namespaceObject. This issue proposes adding support for testing MAP functionality using this feature.

https://kubernetes.io/docs/reference/access-authn-authz/mutating-admission-policy/#patch-type-apply-configuration

Example:

apiVersion: admissionregistration.k8s.io/v1alpha1
kind: MutatingAdmissionPolicy
metadata:
  name: map-with-namespaceObject
spec:
  failurePolicy: Fail
  reinvocationPolicy: IfNeeded
  matchConstraints:
    resourceRules:
    - apiGroups: [""]
      apiVersions: ["v1"]
      operations: ["CREATE"]
      resources: ["pods"]
    namespaceSelector: {}
    objectSelector: {}
  variables:
  - name: test-annotation-val
    expression: "namespaceObject.metadata.annotations['test']"
  mutations:
  - patchType: JSONPatch
    jsonPatch:
      expression: >
        !has(object.metadata.labels) ? [
          JSONPatch{
            op: "add",
            path: "/metadata/labels",
            value: { "k8s.io/test": variables.test-annotation-val}
          }
        ] : [
          JSONPatch{
            op: "add",
            path: "/metadata/labels/" + jsonpatch.escapeKey("k8s.io/test"),
            value: variables.test-annotation-val
          }
        ]

[naoki9911]

kaptest supports testing MAP with namespace objects.
This may be related to the namespace object handling.
Could you provide the tested example ?