Add liveness and readiness probes

• kas: HTTP /liveness and /readiness !149 (merged)
• kas: gRPC https://kubernetes.io/blog/2018/10/01/health-checking-grpc-servers-on-kubernetes/, https://github.com/grpc-ecosystem/grpc-health-probe#example-grpc-health-checking-on-kubernetes With Kubernetes 1.24+, probes can connect via gRPC. We should use that rather than embedding binaries that call those endpoints.
• kas: Update Helm Chart to use ^
• kas: Omnibus?
• agentk: HTTP /liveness and /readiness !263 (merged)
• agentk: update Kustomize package to use ^ !318 (merged)

Both kas and agentk need to have liveness and readiness probes. kas for Helm deployment and agentk for any Kubernetes deployment, obviously.