Helm operator RBAC - use standard approach

The RBAC configuration for the operator is normally set up as part of `cbopcfg`. The helm chart maintains a duplicate of this set up though which means changes can be missed, e.g. https://issues.couchbase.com/browse/K8S-1734?focusedCommentId=528804&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-528804.

https://github.com/couchbase-partners/helm-charts/blob/master/charts/couchbase-operator/templates/operator-deployment.yaml#L81

It would be better to use a single source of truth here and get helm to reuse the same approach.