GRPC mode for konnectivity-server

[kvaps]

Using GRPC is more common configuration for konnectivity-server, it also has some advantages and disadvantages:

pros:

• More common and respectively better tested configuration.
• IP addresses economy. Since we use a single service for apiserver and konnectivity-server it is also reliable workaround for this metallb bug Multiple services with same IP announced multiple times metallb/metallb#558. Remember we use shared-ip annotation which can cause wrong behavior in case if IP shared between the two different workload:
  https://github.com/kvaps/kubernetes-in-kubernetes/blob/ed78b513c73b81e623aeaf82fc0ff7055ff8707a/deploy/helm/kubernetes/templates/apiserver-service.yaml#L15
  https://github.com/kvaps/kubernetes-in-kubernetes/blob/ed78b513c73b81e623aeaf82fc0ff7055ff8707a/deploy/helm/kubernetes/templates/konnectivity-server-service.yaml#L15
• Probably faster communication. There is no network overhead when using unix-sockets instead.

cons:

• konnectivity-server must run as sidecar for apiserver
• Possible complication of supporting both modes in Helm chart