chore(llmobs): extract openai/llmobs tests to separate file

[Yun-Kim]

This PR moves LLMObs tests from the test_openai_v0/v1.py files into test_openai_llmobs.py to ease maintainability for LLMObs tests in the future. No functionality is added/removed.

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

[datadog-datadog-prod-us1]

Software Composition Analysis

We found vulnerabilities in the following libraries (compared df5b752 against a1a0ea7):

• ⚫ pyyaml@0.0.0
• 🔴 gunicorn@20.1.0
• 🔴 certifi@2023.5.7
• 🔴 django@4.2.5
• 🔗 4 more vulnerabilities exist

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: yunkim/llmobs-move-openai-tests
Commit report: d6a8759
Test service: dd-trace-py

✅ 0 Failed, 456 Passed, 864 Skipped, 27m 45.12s Total duration (14m 7.23s time saved)