POTEL 55 - Fix startChild for span that is not in current OTel Context

[adinauer]

📜 Description

OtelSpanFactory now sets the OtelSpanWrappers underlying OTel span as current span in the Context used when creating a new child span so the Context that arrives in the span processor has the correct parent set.

💡 Motivation and Context

Starting a child span from a transaction that wasn't in the current Context lead to multiple transactions being created (one for the transaction and another per span created).

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- POTEL 55 - Fix `startChild` for span that is not in current OTel `Context` ([#3862](https://github.com/getsentry/sentry-java/pull/3862))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against 57ac7d9

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	418.08 ms	469.06 ms	50.98 ms
Size	1.65 MiB	2.31 MiB	672.94 KiB

Previous results on branch: feat/potel-55-non-current-span-start-child

Startup times

Revision	Plain	With Sentry	Diff
8e60d58	369.69 ms	457.40 ms	87.71 ms

App size

Revision	Plain	With Sentry	Diff
8e60d58	1.70 MiB	2.36 MiB	671.45 KiB

[lbloder]

LGTM 👍