bugfix: Fix the permission issue that rbgs controller cannot create rbg

[bcfre]

The rgbs controller needs to create/delete rbg objects according to the rgbs declaration. Currently, the controller lacks the create/delete permission for rgb. The specific error is as follows
{"level":"ERROR","time":"2025-09-02T01:12:47.892Z","caller":"workloads/rolebasedgroupset_controller.go:97","message":"create rbg failed.","controller":"workloads-rolebasedgroupset","controllerGroup":"workloads.x-k8s.io","controllerKind":"RoleBasedGroupSet","RoleBasedGroupSet":{"name":"rbgs-test","namespace":"default"},"namespace":"default","name":"rbgs-test","reconcileID":"7fbf093e-4a74-494e-a182-0f1efef5ffb7","rbgset":{"name":"rbgs-test","namespace":"default"},"error":"create rbg error: rolebasedgroups.workloads.x-k8s.io is forbidden: User \"system:serviceaccount:rbgs-system:rbgs-rbgs-controller-sa\" cannot create resource \"rolebasedgroups\" in API group \"workloads.x-k8s.io\" in the namespace \"default\"","stacktrace":"sigs.k8s.io/rbgs/internal/controller/workloads.(*RoleBasedGroupSetReconciler).Reconcile.func1\n\t/workspace/internal/controller/workloads/rolebasedgroupset_controller.go:97"}

Reproduction method:

1. In the project root directory, execute make deploy to deploy rbg.
2. Execute kubectl apply -f examples/rbgs/rbgs-base.yaml to deploy the test case.
3. Use kubectl logs -n rbgs-system <controller-pod> to view the error log.
4. Run make undeploy to clean up the test resources.

[gujingit]

Thanks for your contribution.