fix(opentelemetry): resolve thread-unsafe iter

[llimllib]

Description

Wrap dd_baggage.items() and otel_baggage.items() with list() in get_current() and attach() to prevent RuntimeError: dictionary changed size during iteration when multiple threads concurrently read and mutate shared baggage dicts via OTel context propagation.

Closes #16523

Testing

added a test and verified that the tests pass

Risks

Adds an additional allocation in get_current and attach

Additional Notes

I made this PR with the assistance of AI, but have read it and think I understand it well enough to suggest it

[chatgpt-codex-connector]

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[brettlangdon]

can you add a release note for this?

https://ddtrace.readthedocs.io/en/stable/releasenotes.html

[datadog-official]

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⚠️ Warnings

🚦 1 Pipeline job failed

System Tests | download-s3-wheels     

🔄 Retry job. This looks flaky and may succeed on retry.

Timed out after 1800s waiting for https://dd-trace-py-builds.s3.amazonaws.com/676f3dbce48d938ae19d31cc30e4517bf5d63e13/index-manylinux2014_x86_64.html

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[llimllib]

DataDog/apm-reliability/dd-trace-py | os tests ubuntu: [3.10] View in Datadog GitLab
🛟 This job is unlikely to succeed on retry. Please review your pipeline configuration.
Failed to fetch repository due to not signed and curl command not found during install attempts.

Is this due to something I did, or something in the CI process? I can't access the link

update: this may be because my commit was unverified? I set up verification and rebased with a signed commit

[llimllib]

The commit is now signed:

$ git log --show-signature -1
commit 676f3dbce48d938ae19d31cc30e4517bf5d63e13 (HEAD -> main, origin/main, origin/HEAD)
Good "git" signature for bill.mill@jellyfish.co with ED25519 key SHA256:Syzy+NnUbX75eh+S705o8d8ZK8LbTZFkB/cjyI>
Author: Bill Mill <bill.mill@jellyfish.co>
Date:   Tue May 19 15:37:41 2026 -0400

and the links in the CI message don't work for me, they seem to be private pages. GitHub shows the commit as verified.

If you want to make the commit yourself because CI won't let me, I won't be offended