ref(replay): Use main thread to schedule capture

[romtsn]

📜 Description

• This reworks the logic to schedule screenshot + VH capture on the main thread using Handler.postDelayed
  • We were anyway posting a message from the capturer thread to the main thread before, so this gets rid of thread context switch all the time, plus ensures we run view checks (like root.width/height) on the main thread right before we capture

A couple of replay examples with the new capture logic:

https://sentry-sdks.sentry.io/explore/replays/699aa0aff2e2496db716274d637f6a33
https://sentry-sdks.sentry.io/explore/replays/d043fb059023427b97fe54f4abf39832

💡 Motivation and Context

💚 How did you test it?

Manually

📝 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	376.06 ms	415.75 ms	39.69 ms
Size	1.58 MiB	2.09 MiB	519.30 KiB