cmd, node, rpc: readd inproc RPC client, expose via node

rpc/ipc.go

@@ -38,7 +38,7 @@ type ipcClient struct {
 // NewIPCClient create a new IPC client that will connect on the given endpoint. Messages are JSON encoded and encoded.
 // On Unix it assumes the endpoint is the full path to a unix socket, and Windows the endpoint is an identifier for a
 // named pipe.
-func NewIPCClient(endpoint string) (*ipcClient, error) {
+func NewIPCClient(endpoint string) (Client, error) {
 	conn, err := newIPCConnection(endpoint)
 	if err != nil {
 		return nil, err