fix(execution): ignore duplicate tx errors in pool

Skip "already known" errors when submitting transactions to Reth's tx pool
since these are not actual failures and the tx is already where it needs to be.

execution.go

@@ -1,7 +1,6 @@
 package execution
 
 import (
-	"bytes"
 	"context"
 	"encoding/hex"
 	"errors"
@@ -238,15 +237,14 @@ func (c *EngineAPIExecutionClient) ExecuteTxs(ctx context.Context, txs []executi
 		}
 	}
 
-	// encode
-	txsPayload := make([][]byte, len(txs))
-	for i, tx := range ethTxs {
-		buf := bytes.Buffer{}
-		err := tx.EncodeRLP(&buf)
+	for _, tx := range ethTxs {
+		err := c.ethClient.SendTransaction(ctx, tx)
 		if err != nil {
-			return execution_types.Hash{}, 0, fmt.Errorf("failed to RLP encode tx: %w", err)
+			// ignore "already known" errors as they're not actual failures
+			if !strings.Contains(err.Error(), "already known") {
+				return execution_types.Hash{}, 0, fmt.Errorf("failed to send transaction: %w", err)
+			}
 		}
-		txsPayload[i] = buf.Bytes()
 	}
 
 	// update forkchoice