fix: Threading issues in binary image cache

[philipphofmann]

📜 Description

Add synchronize to start and stop of SentryBinaryImage crash to avoid threading issues that can lead to crashes.

💡 Motivation and Context

Fixes GH-3462

💚 How did you test it?

Unit tests.

📝 Checklist

You have to check all boxes before merging:

• I reviewed the submitted code.
• 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.
• 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

[codecov]

Codecov Report

Merging #3468 (5139041) into main (4fd1a5d) will decrease coverage by 0.004%.
The diff coverage is 100.000%.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3468       +/-   ##
=============================================
- Coverage   88.965%   88.961%   -0.004%     
=============================================
  Files          525       525               
  Lines        56638     56685       +47     
  Branches     20384     20399       +15     
=============================================
+ Hits         50388     50428       +40     
- Misses        5329      5335        +6     
- Partials       921       922        +1     

Files	Coverage Δ
Sources/Sentry/SentryBinaryImageCache.m	100.000% <100.000%> (ø)
...ests/SentryTests/SentryBinaryImageCacheTests.swift	100.000% <100.000%> (ø)

... and 13 files with indirect coverage changes

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[github-actions]

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Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- Threading issues in binary image cache ([#3468](https://github.com/getsentry/sentry-cocoa/pull/3468))

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