Add stream output for Agent

[Undertone0809]

🚀 Feature Request

Current, ToolAgent cannot use stream mode output. As a ReAct prompt pattern, the intermediate thought steps need to be output. Now we use hooks system to extract middle step, but agent.run(..., stream=True) is simpler.

How to do?

Add stream parameter, use agent.run(..., stream=True).

Reference: https://github.com/InternLM/MindSearch/blob/main/mindsearch/agent/mindsearch_agent.py#L196

[Undertone0809]

ToolAgent + stream mode need to support output schema, but output schema only use in final output now. Need to raise error if stream=True and output_schema is not True.