Apply a CA bundle in cluster-wide proxy for Rosa/OSD

Issue

• Unable add a custom CA bundle:

  $ oc patch proxy/cluster --type=merge --patch='{"spec":{"trustedCA":{"name":"custom-ca"}}}'
  [...]
  Error from server (Prevented from accessing Red Hat managed resources. This is in an effort to prevent harmful actions that may cause unintended consequences or affect the stability of the cluster. If you have any questions about this, please reach out to Red Hat support at https://access.redhat.com/support): admission webhook "regular-user-validation.managed.openshift.io" denied the request: Prevented from accessing Red Hat managed resources. This is in an effort to prevent harmful actions that may cause unintended consequences or affect the stability of the cluster. If you have any questions about this, please reach out to Red Hat support at https://access.redhat.com/support