beacon/blsync: fix requests encoding in engine_newPayloadV4 (ethereum#31775)

This fixes an issue where blocks containing CL requests triggered an
error in the engine API. The encoding of requests used base64 instead of
hex.

Author: fjl

beacon/blsync/engineclient.go

@@ -26,6 +26,7 @@ import (
 	"github.com/ethereum/go-ethereum/beacon/params"
 	"github.com/ethereum/go-ethereum/beacon/types"
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	ctypes "github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/rpc"
@@ -104,7 +105,11 @@ func (ec *engineClient) callNewPayload(fork string, event types.ChainHeadEvent)
 		method = "engine_newPayloadV4"
 		parentBeaconRoot := event.BeaconHead.ParentRoot
 		blobHashes := collectBlobHashes(event.Block)
-		params = append(params, blobHashes, parentBeaconRoot, event.ExecRequests)
+		hexRequests := make([]hexutil.Bytes, len(event.ExecRequests))
+		for i := range event.ExecRequests {
+			hexRequests[i] = hexutil.Bytes(event.ExecRequests[i])
+		}
+		params = append(params, blobHashes, parentBeaconRoot, hexRequests)
 	case "deneb":
 		method = "engine_newPayloadV3"
 		parentBeaconRoot := event.BeaconHead.ParentRoot