[WIP] Enable serialization of agentscope

[DavdGao]

Description

• [x] Serialize the message
• [ ] Serialize the agent

Checklist

Please check the following items before code is ready to be reviewed.

• [ ] Code has passed all tests
• [ ] Docstrings have been added/updated in Google Style
• [ ] Documentation has been updated
• [ ] Code is ready for review