Adds an interface which allows to customize the following
parameters of a controller-manager operator deployment
- change the replica (0/1)
- change the resources (requests/limits) of the manager container

It keeps the current default resource requests as is. For easier
gotemplate it this adds an internal custom struct type, which allows
to just loop over a list of operator.Operator for service operators
and a dedicated instance for the openstack-operator-controller-manager
and the rabbitmq-cluster-operator-manager.

E.g. changing the default cpu limits for the infra operator and
disabling the openstack-baremetal operator would be:
~~~
...
spec:
  operatorOverrides:
  - name: infra
    controllerManager:
      resources:
        limits:
          cpu: 600m
          memory: 2Gi
    replicas: 1
  - name: openstack-baremetal
    replicas: 0
~~~

To add a new service operator has the following high level steps:
- in the openstack_types.go api
  - add a new const with the name
  - add an entry for the defaults in the OperatorList var
  - add the name also to the Enum of the OperatorSpec.Name
- (optional) if any specific env var need be passed to the operator,
  e.g. related images list, or to enable webhooks, check the
  applyOperator() in the openstack_controller.go .

Jira: OSPRH-17785

Signed-off-by: Martin Schuppert <mschuppert@redhat.com>