Add kubeRBACProxy property to support querying in cluster prometheus in openshift

[mittal-ishaan]

• Add kubeRBACProxy property to set KUBE_RBAC_PROXY_ENABLED as true in the env var of the container.
• createPrometheusClusterRoleBinding property to create cluster role binding to grant required permissions to the serviceaccount to query prometheus with kube-rbac-proxy enabled.
• Add the role binding to grant permissions this external prometheus to scrape metrics from kubecost.
• Add a check that both kubeRBACProxy and BearerToken property cannot be set together.

[jessegoodier]

related to #226