Fix TTFD measurement when API called too early

[stefanosiano]

📜 Description

Sentry.reportFullyDisplayed now sets a flag if the ttid is not finished.
When the TTID finishes, if the flag is set, the TTFD is finished as well

💡 Motivation and Context

Fixes #3384

💚 How did you test it?

Unit 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	432.29 ms	480.24 ms	47.95 ms
Size	1.58 MiB	2.22 MiB	655.02 KiB