[K8s operator] Cluster and Namespaced services support

[CarlosLanderas]

What this PR does / why we need it:

Add support for Cluster and Namespaced scopes.

The scope field (Cluster or Namespaced) is mandatory and will specify to the operator whether it should watch for healthchecks services in the same namespace where the UI resource is created or watch to all services in all namespaces.

If you wan't to have different UI's for different namespaced services you should use Namespaced

If you wan't to have a single UI that monitors all the healthchecks from the cluster you should use Cluster

Note: The UI resources created by the operator (deployment, service, configmap, secret, etc) will always be created in the metadata specified namespace.

spec:
  name: healthchecks-ui
  scope: Namespaced #The UI will be created at specified namespace (demo) and will watch healthchecks services in demo namespace only
  #scope: Cluster The UI will be created at specified namespace (demo) but will watch healthcheck services across all namespaces
  servicesLabel: HealthChecks

Which issue(s) this PR fixes: #575