Add `as_server` command and add `server_id`

[pan-x-c]

Description

1. Extract the agent server related modules from the rpc_agent.py into agentscope.server package(launcher.py and servicer.py)
2. Add as_server command to setup.py
3. Add server_id to identify a server instance
4. update the distribution part of the tutorial

Checklist

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

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