Provide static IP-address for LoadBalancer

We allow users to expose database clusters and its components through various Service Types, including load balancers.

There is a use case, where user wants to have a static IP-address for the load balancer. This also includes internal load balancers in the clouds.

This can be done through `loadBalancerIP` field.

 spec:
  loadBalancerIP: 1.2.3.4
  type: LoadBalancer

• We are going to pass through loadBalancerIP parameter to the service spec.
• If exposeType is not LoadBalancer, we still pass through loadBalancerIP parameter to the spec
• We rely on Kubernetes logic to parse and make a decision about loadBalancerIP valid inputs
  • We return the error if service creation fails
• We are not adding loadBanacerIP to pgReplicas exposure, as these are exposed as a service per Pod.
• We are going to introduce loadBalancerIP into the custom resource in the following places:

 spec:
   pgPrimary:
     expose:
       serviceType: LoadBalancer
       loadBalancerIP: 1.2.3.4
   pgReplicas:
     expose:
       serviceType: LoadBalancer
   pgBouncer:
     expose:
       serviceType: LoadBalancer
       loadBalancerIP: 1.2.3.4