Tool Guide for documenting how to use tools across both AgentChat and Core

[ekzhu]

The guide should be in Extensions->Tool Guide. The guide should cover:

1. FunctionTool:

• How to define them as Python function (both sync and async)
• How does it work: function gets inspected and automatically generates the JSON schema.
• Recommendation on input parameter design: use simple and as few parameters as possible, avoid nested types like dictionaries.
• Recommendation on return type: use serializable types to better integrate with models -- use string as much as possible.
• Recommendation on type hinting and doc string

2. Built-in Tools: a listing pointing to existing built in tools in the API doc.
3. Custom BaseTool implementation:

• An example to show how to create one.
• Consideration for serializable configuration.

There are existing docs in AgentChat and Core mentioning tools:

• AgentChat: https://microsoft.github.io/autogen/stable/user-guide/agentchat-user-guide/tutorial/agents.html#using-tools
• Core: https://microsoft.github.io/autogen/stable/user-guide/core-user-guide/components/tools.html

We should move the main content from these docs that regards to tools specifically to the Tool Guide. Leave content regarding to using tools as part of agent.