Leverage gRPC external cloud provider instead of forking and maintaining upstream repository

[unmarshall]

What would you like to be added:
Upstream cluster-autoscaler provides a way for custom cloud providers to plug in (out-of-tree) to CA via gRPC external cloud provider. We should do a POC to learn on how to get this setup done, to also learn its issues/short comings and in the end to take a decision on whether this would be a feasible solution for MCM as a cloud provider.

Why is this needed:
Eliminates the need to maintain a fork of the upstream cluster-autoscaler repo. We can even think of moving this MCM cloud provider as part of the MCM pod. Ideally we should just have 2 containers in the MCM pod:

1. MCM core + MCM provider extension into one container
2. Side car: which provides the custom cloud provider for cluster-autoscaler.