[Feature Request] Add gRPC heath check via grpc_health_probe

[underrun]

Currently we are using successful tcp connection as a proxy for health in kubernetes. Instead we can use grpc_health_probe to check health using grpc.

[robholland]

Now built-in to kubernetes: https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/#define-a-grpc-liveness-probe