Fix TxPool.PackTxsWithBytes to use encoded transaction size instead of unsafe.Sizeof

[1654574171]

Note

I noticed this might be a potential issue — please let me know if my understanding is off.

Summary

This PR fixes TxPool.PackTxsWithBytes so that it uses the encoded transaction size
instead of unsafe.Sizeof(*tx) when deciding how many transactions to pack.

Using unsafe.Sizeof only accounts for the in-memory struct header size and ignores
the actual payload stored behind slices, strings, etc. This can lead to significant
underestimation of the real block/tx batch size.

Changes

// Pack transaction for a proposal (use 'BlocksizeInBytes' to control)
func (txpool *TxPool) PackTxsWithBytes(max_bytes int) []*Transaction {
	txpool.lock.Lock()
	defer txpool.lock.Unlock()

	txNum := len(txpool.TxQueue)
	currentSize := 0
	for tx_idx, tx := range txpool.TxQueue {
        //currentSize += int(unsafe.Sizeof(*tx)) 
		currentSize += len(tx.Encode())
		if currentSize > max_bytes {
			txNum = tx_idx
			break
		}
	}

	txs_Packed := txpool.TxQueue[:txNum]
	txpool.TxQueue = txpool.TxQueue[txNum:]
	return txs_Packed
}