p2p/rlpx: optimize XOR operation using bitutil.XORBytes (ethereum#32217)

Replace manual byte-by-byte XOR implementation with the optimized
bitutil.XORBytes function. This improves performance by using word-sized
operations on supported architectures while maintaining the same
functionality. The optimized version processes data in bulk rather than
one byte at a time

---------

Co-authored-by: Felix Lange <fjl@twurst.com>

Author: 2 people

p2p/rlpx/rlpx.go

@@ -33,6 +33,7 @@ import (
 	"net"
 	"time"
 
+	"github.com/ethereum/go-ethereum/common/bitutil"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/crypto/ecies"
 	"github.com/ethereum/go-ethereum/rlp"
@@ -676,8 +677,6 @@ func exportPubkey(pub *ecies.PublicKey) []byte {
 
 func xor(one, other []byte) (xor []byte) {
 	xor = make([]byte, len(one))
-	for i := 0; i < len(one); i++ {
-		xor[i] = one[i] ^ other[i]
-	}
+	bitutil.XORBytes(xor, one, other)
 	return xor
 }