ci: move build_docs to gitlab

[emmettbutler]

This change moves the build_docs CI job to gitlab as part of the ongoing migration away from circleci.

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:

.gitlab-ci-local/.gitignore                                             @DataDog/apm-core-python
.circleci/config.templ.yml                                              @DataDog/python-guild @DataDog/apm-core-python
.gitlab/package.yml                                                     @DataDog/python-guild @DataDog/apm-core-python
.gitlab/tests.yml                                                       @DataDog/python-guild @DataDog/apm-core-python
scripts/gen_circleci_config.py                                          @DataDog/apm-core-python
scripts/gen_gitlab_config.py                                            @DataDog/apm-core-python

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: emmett.butler/gitlab-build-docs
Commit report: 1dff133
Test service: dd-trace-py

✅ 0 Failed, 43 Passed, 290 Skipped, 50.81s Total duration (5m 33.99s time saved)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-26 21:07:32

Comparing candidate commit 1dff133 in PR branch emmett.butler/gitlab-build-docs with baseline commit 2aa4ffb in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 418 metrics, 2 unstable metrics.