[FEATURE] Allow helm read-only RBAC configuration toggle

[Dhouti]

The defaults are extremely permissive.

Adding a toggle to remove the update/delete verbs would be nice.
In the meantime i cannot use this helm chart as is. :(

Current ClusterRole:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: {{ include "kagent.fullname" . }}-cluster-admin-role
  labels:
    {{- include "kagent.labels" . | nindent 4 }}
rules:
- apiGroups: ["*"]
  resources: ["*"]
  verbs: ["*"]
- nonResourceURLs: ["*"]
  verbs: ["*"]