Save `ckbVirtualTxResult` in the code examples

[Flouse]

Important

It's recommended to save the rgbpp_ckb_tx_virtual locally before the isomophic transactions are finalized.

• Let's follow this suggestion in examples/rgbpp/*, save all the ckbVirtualTxResult into a log file.
• Also add some comments to remind developers to follow this suggestion.

[Dawn-githup]

Important

It's recommended to save the rgbpp_ckb_tx_virtual locally before the isomophic transactions are finalized.

• Let's follow this suggestion in examples/rgbpp/*, save all the ckbVirtualTxResult into a log file.
• Also add some comments to remind developers to follow this suggestion.

I have implemented according to the description, please help review if it is reasonable. Thank you.
#193