l2geth: Fix state dumper (#3794)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

.changeset/real-deers-heal.md

+---
+'@eth-optimism/l2geth': patch
+---
+
+Fix state dumper

l2geth/statedumper/dumper_test.go

+package statedumper
+
+import (
+	"github.com/ethereum-optimism/optimism/l2geth/common"
+	"io"
+	"os"
+	"testing"
+)
+
+func TestFileStateDumper(t *testing.T) {
+	f, err := os.CreateTemp("", "")
+	if err != nil {
+		t.Fatalf("error creating file: %v", err)
+	}
+	err = os.Setenv("L2GETH_STATE_DUMP_PATH", f.Name())
+	if err != nil {
+		t.Fatalf("error setting env file: %v", err)
+	}
+	dumper := NewStateDumper()
+	addr := common.Address{19: 0x01}
+	dumper.WriteETH(addr)
+	dumper.WriteMessage(addr, []byte("hi"))
+	_, err = f.Seek(0, 0)
+	if err != nil {
+		t.Fatalf("error seeking: %v", err)
+	}
+	data, err := io.ReadAll(f)
+	if err != nil {
+		t.Fatalf("error reading: %v", err)
+	}
+	dataStr := string(data)
+	if dataStr != "ETH|0x0000000000000000000000000000000000000001\nMSG|0x0000000000000000000000000000000000000001|6869\n" {
+		t.Fatalf("invalid data. got: %s", dataStr)
+	}
+}