Replace most marshaling with codegen

lib/cborrpc/rpc.go

@@ -4,11 +4,15 @@ import (
 	"io"
 
 	cbor "github.com/ipfs/go-ipld-cbor"
+	cbg "github.com/whyrusleeping/cbor-gen"
 )
 
 const MessageSizeLimit = 1 << 20
 
 func WriteCborRPC(w io.Writer, obj interface{}) error {
+	if m, ok := obj.(cbg.CBORMarshaler); ok {
+		return m.MarshalCBOR(w)
+	}
 	data, err := cbor.DumpObject(obj)
 	if err != nil {
 		return err
@@ -19,5 +23,8 @@ func WriteCborRPC(w io.Writer, obj interface{}) error {
 }
 
 func ReadCborRPC(r io.Reader, out interface{}) error {
+	if um, ok := out.(cbg.CBORUnmarshaler); ok {
+		return um.UnmarshalCBOR(r)
+	}
 	return cbor.DecodeReader(r, out)
 }