chore: remove vendored contextvars module

[taegyunkim]

contextvars was added in version 3.7.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, 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

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/internal/compat.py                                              @DataDog/python-guild @DataDog/apm-core-python
ddtrace/internal/coverage/code.py                                       @DataDog/apm-core-python @datadog/ci-app-libraries
ddtrace/vendor/__init__.py                                              @DataDog/apm-core-python

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-13 15:42:09

Comparing candidate commit ac0e9b0 in PR branch taegyunkim/remove-vendor-contextvars with baseline commit 30e3b76 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 394 metrics, 2 unstable metrics.

[emmettbutler]

I'll do a proper review once tests are passing

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: taegyunkim/remove-vendor-contextvars
Commit report: ac0e9b0
Test service: dd-trace-py

✅ 0 Failed, 87 Passed, 1468 Skipped, 4m 23.21s Total duration (35m 39.34s time saved)

[taegyunkim]

@emmettbutler ready for a review, can you take a look?