[FEATURE] Agent `to_tool` method

[Unshure]

Problem Statement

I would like to easily pass an agent as a tool to anther agent with as little boiler plate code as possible.

Proposed Solution

researcher = Agent(system_prompt="You research topics")

manager = Agent(system_prompt="You delegate to the researcher", tools=[researcher.to_tool()])

The to_tool method returns an AgentTool instance for invoking an agent as a tool. It will initially take in a single parameter named preserve_context: bool to determine if each time the agent as a tool is invoked, if the previous conversation context should be wiped or not.

Use Case

Make it easier to use one agent as a tool for another agent.

Alternatives Solutions

researcher = Agent(system_prompt="You research topics")

manager = Agent(system_prompt="You delegate to the researcher", tools=[researcher])

Allow an agent to be passed in directly to the tool array. We can do this as a follow up, but for configuration, we want to have a specific method on the agent class that enables this behavior.

Additional Context

No response