Implement support for gRPC readiness probes

[rhmdnd]

just a suggestion, I'm not even sure if OCP enables grpc probes feature by default (it's beta since 1.24), but if it does, then we might want to add a readiness probe and a heath probe: https://kubernetes.io/blog/2022/05/13/grpc-probes-now-in-beta/

Originally posted by @jhrozek in #163 (comment)