Introduce support for LoadBalancerClass

[bsctl]

It would be useful to introduce support for LoadBalancerClass, in TCP service which allows multiple load balancer implementations to co-exist on the Management Cluster. If set, it is assumed that a load balancer implementation is watching for Services with a matching class. Any default load balancer implementation (e.g. cloud providers) should ignore Services that set this field. This field can only be set when creating or updating a Service to type 'LoadBalancer'. Ignored when other service types are userd.

  apiVersion: kamaji.clastix.io/v1alpha1
  kind: TenantControlPlane
  metadata:
    name: #name
    namespace: #namespace
  spec:
    dataStore: default
    controlPlane:
      deployment:
        replicas: 2
      service:
        serviceType: LoadBalancer
        # loadBalancerClass: <class>   <<< 

[prometherion]

Implemented with #620