New kubelet gRPC API with endpoint returning local pods information

This KEP proposes a new Kubelet gRPC API with an endpoint that returns local Pod information, including the full PodSpec and status. Serving this information from Kubelet on a node increases reliability and reduces load on the Kubernetes API Server and network traffic outside the node. Connectivity issues between the node and control plane should not impact workloads that depend on Pod state information. The full PodSpec may contain sensitive information, so access to this API is secured by restricting the UNIX socket to local admin users only.