Expose custom cxa throw and rethrow calls to Unity

[munkiki7]

📜 Description

I have added custom calls that can be later used by Unity SDK for capturing C++ exceptions on iOS.
Also, when the current exception is NULL (during the std::terminate call) the sentrycrashsc_initSelfThread call is made to enrich the stack trace.

💡 Motivation and Context

The fix is related to this issue.

💚 How did you test it?

I have added the code to the Unity SDK that calls these new exposed functions using the dlsym search:

📝 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

[philipphofmann]

This change makes sense to me, but I think someone of @getsentry/owners-native should have a look at this proposal, because my CPP on that topic isn't the best. @armcknight, maybe you could also have a look please?

[Swatinem]

lgtm

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 35 lines in your changes are missing coverage. Please review.

Project coverage is 90.874%. Comparing base (c6b920a) to head (0b7dd7b).
Report is 4 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3996       +/-   ##
=============================================
+ Coverage   90.850%   90.874%   +0.024%     
=============================================
  Files          594       594               
  Lines        46494     46607      +113     
  Branches     16641     16690       +49     
=============================================
+ Hits         42240     42354      +114     
- Misses        4071      4183      +112     
+ Partials       183        70      -113     

Files	Coverage Δ
...rding/Monitors/SentryCrashMonitor_CPPException.cpp	20.408% <0.000%> (-3.122%)	⬇️

... and 45 files with indirect coverage changes

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[philipphofmann]

I added a changelog entry and tested this with the macOS sample app. Previously, the SDK didn't catch the crash report for the following code

void
Sentry::CppSample::rethrowNoActiveCPPException(void)
{
    // Rethrowing an exception when there is no active exception will lead to std::terminate being
    // called.
    throw;
}

No, it does, see screenshot:

Thanks a lot, @munkiki7, LGTM.

[munkiki7]

Glad to be helpful, @philipphofmann