Fix ANR on dropped uncaught exception events

[romtsn]

📜 Description

We were trying to flush the event to disk, even though the event was dropped and we never called markFlushed, hence it was blocking for 15seconds everytime the event is dropped 🙈

💡 Motivation and Context

Closes #2346

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• No breaking changes

🔮 Next steps

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	354.80 ms	392.86 ms	38.06 ms
Size	1.73 MiB	2.32 MiB	610.02 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
f809aac	301.51 ms	346.60 ms	45.09 ms
a04f788	321.78 ms	354.12 ms	32.35 ms
38e4f11	358.20 ms	433.73 ms	75.53 ms
507f924	342.51 ms	402.65 ms	60.14 ms
90e9745	314.68 ms	357.28 ms	42.60 ms
7597ded	289.60 ms	339.69 ms	50.09 ms

App size

Revision	Plain	With Sentry	Diff
f809aac	1.73 MiB	2.32 MiB	608.63 KiB
a04f788	1.73 MiB	2.32 MiB	609.88 KiB
38e4f11	1.73 MiB	2.32 MiB	609.82 KiB
507f924	1.73 MiB	2.32 MiB	609.95 KiB
90e9745	1.73 MiB	2.32 MiB	608.63 KiB
7597ded	1.73 MiB	2.32 MiB	609.88 KiB