Extend tests to ensure default integrations are registered

[markushi]

📜 Description

As another follow-up to #4449, we want to ensure that integrations are registered, both in cases of foreground or background init.

💡 Motivation and Context

SDKs, steady as a rock.

#skip-changelog

💚 How did you test it?

Added tests.

📝 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]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	403.96 ms	482.82 ms	78.86 ms
Size	1.58 MiB	2.08 MiB	510.93 KiB

Previous results on branch: markushi/chore/extend-sdk-init-tests

Startup times

Revision	Plain	With Sentry	Diff
76f3c68	434.92 ms	493.54 ms	58.62 ms
d156253	425.88 ms	492.06 ms	66.18 ms
26c62af	407.98 ms	449.69 ms	41.71 ms

App size

Revision	Plain	With Sentry	Diff
76f3c68	1.58 MiB	2.08 MiB	510.84 KiB
d156253	1.58 MiB	2.08 MiB	510.84 KiB
26c62af	1.58 MiB	2.08 MiB	510.84 KiB

[romtsn]

dope!

[stefanosiano]

nice!