test(otel): cover OTEL_METRIC_EXPORT_TIMEOUT parametrically

[vpellan]

Motivation

Add specification-based parametric coverage for OTEL_METRIC_EXPORT_TIMEOUT.

Tracks APMAPI-2397.

Changes

• Test representative values, unset, empty and default values, and configuration
  precedence.
• Declare support in every tracer manifest from the configuration registry.
• Declare spec default as irrelevant for all SDKs but PHP

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner.
   • Framework is modified, or non obvious usage of it -> get a review from
     R&P team

🚀 Once your PR is reviewed and the CI green, you can merge it!

🛏 #apm-shared-testing 🛏

Reviewer checklist

• Anything but tests/ or manifests/ is modified? I have the approval
  from R&P team
• A docker base image is modified?
  • The relevant build-XXX-image label is present
• A scenario is added, removed or renamed?
  • Get a review from
    R&P team

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-09T12:23:28.345135Z	4ecff7c	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[github-actions]

CODEOWNERS have been resolved as:

tests/parametric/otel_env_vars/test_otel_metric_export_timeout.py       @DataDog/system-tests-reviewers
manifests/cpp.yml                                                       @DataDog/system-tests-reviewers
manifests/dotnet.yml                                                    @DataDog/system-tests-reviewers
manifests/golang.yml                                                    @DataDog/system-tests-reviewers
manifests/java.yml                                                      @DataDog/system-tests-reviewers
manifests/nodejs.yml                                                    @DataDog/system-tests-reviewers
manifests/php.yml                                                       @DataDog/system-tests-reviewers
manifests/python.yml                                                    @DataDog/system-tests-reviewers
manifests/ruby.yml                                                      @DataDog/system-tests-reviewers
manifests/rust.yml                                                      @DataDog/system-tests-reviewers

[datadog-datadog-prod-us1-2]

✅ All CI checks and tests passed.

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 016ba6f | Docs | View more details | Give us feedback!}

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 4ecff7c4ff

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".