feat: add tool use to agent interface

[micpst]

Feature description

Add tool use to Agent interface.

llm = LiteLLM(model_name="gpt-4o-2024-08-06", use_structured_output=True)
agent = Agent(llm=llm, prompt=AnimalPrompt, tools=[get_weather])
await agent.run(AnimalPromptInput(animal="cat"))

Agents should:

• call tools by itself when requested by the model
• notify in realtime (yield) events, for example notify about the tool call