Add tool calling for Openai (compatiable) agent and then using Openai (compatiable) agent as SupervisorAgent (python)

[ycysuk]

Issue Link (REQUIRED)

Fixes #363

Summary

Changes

Add tool calling for Openai (compatiable) agent :

python/src/agent_squad/types/types.py
python/src/agent_squad/utils/tools.py
python/src/agent_squad/agents/openai_agent.py

Using Openai (compatiable) agent as SupervisorAgent:
python/src/agent_squad/agents/supervisor_agent.py

and also modified an OpenAIAgent as SupervisorAgent demo:
examples/supervisor-mode/openaiagent-as-supervisoragent-demo

User experience

Checklist

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• I have performed a self-review of this change
• Changes have been tested
• Changes are documented
• I have linked this PR to an existing issue (required)

Is this a breaking change?

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

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