MetalLB: secondary - 3rd party - LB support with metalLB as default LB

1. Proposed title of this feature request
MetalLB: Support LoadBalancerClass with MetalLB, MetalLB Operator in OCP

2. What is the nature and description of the request?
Beginning with k8s v1.22 multiple LoadBalancer Controllers can be used in a single cluster. This allows either default LoadBalancer or other LoadBalancers to be selected by adding spec.loadBalancerClass to the service definition.

Franck had confirmed that loadBalancerClass change in MetalLB (upstream) is part of OCP 4.11 but it is not usable. included comments from Franck below

"The code is part of OCP4.11 but is not usable as https://github.com/metallb/metallb-operator/issues/267 (we have not planned to work on it, but upstream may or may not pick it up, and also this would need to be added in MetalLB Operators) is missing."

3. Why does the customer need this? (List the business requirements here)
Samsung wants to use MetalLB, however they have one specific use case where they need two things 1) The ability to ingress on an egress IP (which we have coming in 4.13), AND true survivability (no connection reset) for SCTP sessions during failover (Our solution does not provide this). Samsungs in-house LB CNLB provides both of these, but comes with other complications for routing and implementation in the cluster. Samsung is looking to use MetalLB as their DEFAULT LB, and use CNLB for the single use case where they need these two features.

Samsung is already using their CNLB Load Balancer in production deployments today.

4. List any affected packages or components.
MetalLB, MetalLB Operator