Add data from transaction root span to trace.context.data

[lbloder]

:scroll: Description

Add root span data to traceContext when SentryTransaction is created

:bulb: Motivation and Context

Fixes #3626

:green_heart: How did you test it?

Modified existing serialization tests

:pencil: 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.

:crystal_ball: Next steps