feat: Propagate TraceID to the Cocoa SDK

[bitsandfoxes]

Proof of concept. It's possible to set the trace ID on the scope and also to retrieve it but events created by crashes do not seem to take the trace ID from there.

[github-actions]

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

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📖	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

- Propagate `TraceID` to the Cocoa SDK ([#1990](https://github.com/getsentry/sentry-unity/pull/1990))

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[bitsandfoxes]

Superseded by #2106