core: reduce alloc (#33576)

inside tx.GasPrice()/GasFeeCap()/GasTipCap() already new a big.Int.  
bench result:  
```
goos: darwin
goarch: arm64
pkg: github.com/ethereum/go-ethereum/core
cpu: Apple M4
                        │   old.txt   │               new.txt               │
                        │   sec/op    │   sec/op     vs base                │
TransactionToMessage-10   240.1n ± 7%   175.1n ± 7%  -27.09% (p=0.000 n=10)

                        │  old.txt   │              new.txt               │
                        │    B/op    │    B/op     vs base                │
TransactionToMessage-10   544.0 ± 0%   424.0 ± 0%  -22.06% (p=0.000 n=10)

                        │  old.txt   │              new.txt               │
                        │ allocs/op  │ allocs/op   vs base                │
TransactionToMessage-10   17.00 ± 0%   11.00 ± 0%  -35.29% (p=0.000 n=10)
```
benchmark code:  

```
// Copyright 2025 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package core

import (
	"math/big"
	"testing"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/crypto"
	"github.com/ethereum/go-ethereum/params"
)

// BenchmarkTransactionToMessage benchmarks the TransactionToMessage function.
func BenchmarkTransactionToMessage(b *testing.B) {
	key, _ := crypto.GenerateKey()
	signer := types.LatestSigner(params.TestChainConfig)
	to := common.HexToAddress("0x000000000000000000000000000000000000dead")
	
	// Create a DynamicFeeTx transaction
	txdata := &types.DynamicFeeTx{
		ChainID:   big.NewInt(1),
		Nonce:     42,
		GasTipCap: big.NewInt(1000000000),  // 1 gwei
		GasFeeCap: big.NewInt(2000000000),  // 2 gwei
		Gas:       21000,
		To:        &to,
		Value:     big.NewInt(1000000000000000000), // 1 ether
		Data:      []byte{0x12, 0x34, 0x56, 0x78},
		AccessList: types.AccessList{
			types.AccessTuple{
				Address:     common.HexToAddress("0x0000000000000000000000000000000000000001"),
				StorageKeys: []common.Hash{
					common.HexToHash("0x0000000000000000000000000000000000000000000000000000000000000001"),
				},
			},
		},
	}
	tx, _ := types.SignNewTx(key, signer, txdata)
	baseFee := big.NewInt(1500000000) // 1.5 gwei

	b.ResetTimer()
	b.ReportAllocs()
	for i := 0; i < b.N; i++ {
		_, err := TransactionToMessage(tx, signer, baseFee)
		if err != nil {
			b.Fatal(err)
		}
	}
}
l
```

core/state_transition.go

@@ -177,9 +177,9 @@ func TransactionToMessage(tx *types.Transaction, s types.Signer, baseFee *big.In
 	msg := &Message{
 		Nonce:                 tx.Nonce(),
 		GasLimit:              tx.Gas(),
-		GasPrice:              new(big.Int).Set(tx.GasPrice()),
+		GasPrice:              tx.GasPrice(),
-		GasFeeCap:             new(big.Int).Set(tx.GasFeeCap()),
+		GasFeeCap:             tx.GasFeeCap(),
-		GasTipCap:             new(big.Int).Set(tx.GasTipCap()),
+		GasTipCap:             tx.GasTipCap(),
 		To:                    tx.To(),
 		Value:                 tx.Value(),
 		Data:                  tx.Data(),