feat(openai): add support for parallel function calls

[achang97]

#1427

• Add support for multiple/parallel tool calls for OpenAI
• Add ID to function object

• 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.

[nirga]

Thanks @achang97! Looks good! Can you take a look at the failing test?