[QA] Load lazy fields on init in the background

[stefanosiano]

📜 Description

Lazy fields in SentryOptions are now loaded on init in the background

💡 Motivation and Context

Instead of loading the options fields backed by LazyEvaluator when needed, we do it in the background as soon as we can. When the SDK will need these fields, they will be already cached and ready to use

This improved init() by ~5-15ms in profileable builds

💚 How did you test it?

📝 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.

🔮 Next steps

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	421.84 ms	463.94 ms	42.10 ms
Size	1.70 MiB	2.35 MiB	667.95 KiB