Enable ThreadLocalAccessor for Spring Boot 3 WebFlux by default

[adinauer]

📜 Description

Change default for sentry.reactive.thread-local-accessor-enabled when the property is missing to use ThreadLocalAccessor by default.

💡 Motivation and Context

Closes #4020

💚 How did you test it?

📝 Checklist

• 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.
• I updated the wizard 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]

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

Generated by 🚫 dangerJS against 86052e4

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	397.11 ms	426.00 ms	28.89 ms
Size	1.65 MiB	2.31 MiB	677.57 KiB

Previous results on branch: feat/webflux-thread-local-accessor-default

Startup times

Revision	Plain	With Sentry	Diff
4281f14	409.46 ms	527.63 ms	118.17 ms

App size

Revision	Plain	With Sentry	Diff
4281f14	1.65 MiB	2.31 MiB	677.57 KiB

[lbloder]

LGTM 👍