fix(file-io): Do not leak SentryFileInputStream/SentryFileOutputStream descriptors and channels

[romtsn]

📜 Description

• We forgot to call close in SentryFIOStream, and were just calling delegate.close but the associated channels and file descriptors were still leaking for our streams
• Changed addAttachment sample so it uses a FileChannel (this is how I managed to reproduce the strict mode violation)

💡 Motivation and Context

Closes #2905

💚 How did you test it?

Manually + automated

📝 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	455.44 ms	477.88 ms	22.44 ms
Size	1.58 MiB	2.22 MiB	655.17 KiB

Previous results on branch: rz/fix/leaked-closable-sentry-fios

Startup times

Revision	Plain	With Sentry	Diff
09b189a	482.93 ms	520.49 ms	37.56 ms

App size

Revision	Plain	With Sentry	Diff
09b189a	1.58 MiB	2.22 MiB	655.17 KiB