feat: Add maxAttachmentSize to SentryOptions

[philipphofmann]

📜 Description

Drop attachments that are larger than the specified maxAttachmentSize in SentryOptions.

💡 Motivation and Context

We want to give the users of the SDK the possibility to drop large attachments.

💚 How did you test it?

Unit tests.

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the CHANGELOG
• I updated the docs if needed
• Review from the native team if needed
• No breaking changes

🔮 Next steps

[codecov-io]

Codecov Report

Merging #887 (5334690) into master (2d525f4) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #887      +/-   ##
==========================================
- Coverage   94.37%   94.37%   -0.01%     
==========================================
  Files          75       75              
  Lines        3360     3394      +34     
==========================================
+ Hits         3171     3203      +32     
- Misses        189      191       +2     

Impacted Files	Coverage Δ
Sources/Sentry/SentryEnvelope.m	92.46% <100.00%> (+0.15%)	⬆️
Sources/Sentry/SentryHttpTransport.m	95.45% <100.00%> (+0.10%)	⬆️
Sources/Sentry/SentryOptions.m	100.00% <100.00%> (ø)

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[bruno-garcia]

Lgtm but I think 5 mb is too small.