feat(llmobs): capture more model parameters in openai chat/completion spans

[Yun-Kim]

This PR captures more model/input parameters in OpenAI chat/completion spans. Currently we only capture temperature and max_tokens, but there are plenty of other parameters that we can capture as part of the request metadata to LLM Observability.

Checklist

• [ ] Change(s) are motivated and described in the PR description
• [ ] Testing strategy is described if automated tests are not included in the PR
• [ ] Risks are described (performance impact, potential for breakage, maintainability)
• [ ] Change is maintainable (easy to change, telemetry, documentation)
• [ ] Library release note guidelines are followed or label changelog/no-changelog is set
• [ ] Documentation is included (in-code, generated user docs, public corp docs)
• [ ] Backport labels are set (if applicable)
• [ ] If this PR changes the public interface, I've notified @DataDog/apm-tees.

Reviewer Checklist

• [ ] Title is accurate
• [ ] All changes are related to the pull request's stated goal
• [ ] Description motivates each change
• [ ] Avoids breaking API changes
• [ ] Testing strategy adequately addresses listed risks
• [ ] Change is maintainable (easy to change, telemetry, documentation)
• [ ] Release note makes sense to a user of the library
• [ ] Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• [ ] Backport labels are set in a manner that is consistent with the release branch maintenance policy