libs/log: format []byte as hexidecimal string (uppercased) (#5960)

Closes: #5806 

Co-authored-by: Lanie Hei <heixx011@umn.edu>

mempool/clist_mempool.go

@@ -776,7 +776,7 @@ func TxKey(tx types.Tx) [TxKeySize]byte {
 	return sha256.Sum256(tx)
 }
 
-// txID is the hex encoded hash of the bytes as a types.Tx.
-func txID(tx []byte) string {
-	return fmt.Sprintf("%X", types.Tx(tx).Hash())
+// txID is a hash of the Tx.
+func txID(tx []byte) []byte {
+	return types.Tx(tx).Hash()
 }