Added cost metrics for openai in init.py and chat_wrappers.py

[apuwk]

Towards #1042

Added cost metrics for OpenAI. Confused because the tests aren't running properly and I'm not sure where I am going wrong.

• [ ] I have added tests that cover my changes.
• [ ] If adding a new instrumentation or changing an existing one, I've added screenshots from some observability platform showing the change.
• [ ] PR name follows conventional commits format: feat(instrumentation): ... or fix(instrumentation): ....
• [ ] (If applicable) I have updated the documentation accordingly.

[CLAassistant]

All committers have signed the CLA.