Replace RestTemplate with OkHttp for system tests

[adinauer]

#skip-changelog

📜 Description

Replace RestTemplate with OkHttp for system tests

💡 Motivation and Context

RestTemplates raw status code is deprecated so this would cause some headaches when adding support for Spring 7 (Spring Boot 4). Replacing it should get rid of the problem.

💚 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 941f1d5

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	427.41 ms	462.78 ms	35.37 ms
Size	1.58 MiB	2.21 MiB	641.82 KiB

Baseline results on branch: feat/add-distributed-tracing-system-tests-to-more-modules

Startup times

Revision	Plain	With Sentry	Diff
b081a72	427.87 ms	490.38 ms	62.50 ms

App size

Revision	Plain	With Sentry	Diff
b081a72	1.58 MiB	2.21 MiB	641.83 KiB