Add minimal functionality test for k8s control plane

Basic functionality test that sends the bootstrap RPC call,
waits for the k8s control plane to come up and runs a simple
kubectl command (that is expected to fail).

Adds reflection to the server to make grpc_cli easier to use.

Test Plan:
Ran `:launch` (because we modified its config) and `:test_boot`,
saw a nicely booted k8s cluster:

{P90}

X-Origin-Diff: phab/D275
GitOrigin-RevId: fe01e3f3ed09877aa76c15946664c9d9bdc4751b
diff --git a/core/internal/kubernetes/auth.go b/core/internal/kubernetes/auth.go
index afc51c1..89ae6dc 100644
--- a/core/internal/kubernetes/auth.go
+++ b/core/internal/kubernetes/auth.go
@@ -351,7 +351,7 @@
 func makeLocalKubeconfig(ca, cert, key []byte) ([]byte, error) {
 	kubeconfig := configapi.NewConfig()
 	cluster := configapi.NewCluster()
-	cluster.Server = "https://localhost:6443"
+	cluster.Server = "https://127.0.0.1:6443"
 	cluster.CertificateAuthorityData = pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: ca})
 	kubeconfig.Clusters["default"] = cluster
 	authInfo := configapi.NewAuthInfo()