fix: Crash for Custom ViewController init on iOS 15

[philipphofmann]

📜 Description

Swizzle all custom ViewControllers. First, fetch all subclasses of ViewController and then swizzle them. As there is no straightforward way to get all sub-classes in Objective-C, the code first retrieves all classes in the runtime, iterates over all classes, and checks for every class if UIViewController is a parent. Cause loading all classes can take a few milliseconds, do this on a background thread, which should be fine because the SDK swizzles the root view controller and its children.
Previously, the code intercepted the ViewController initializers with swizzling to swizzle the lifecycle methods. This approach led to ViewControllers crashing when using a convenience initializer, see GH-1355. The error occurred because our swizzling logic adds the method to swizzle if the class doesn't implement it. It seems like adding an extra initializer causes problems with the rules for initialization in Swift, see https://docs.swift.org/swift-book/LanguageGuide/Initialization.html#ID216.

💡 Motivation and Context

GH-1355

💚 How did you test it?

Unit tests and on a real device.

I also profiled swizzling the view controllers on https://github.com/home-assistant/iOS, which has a couple of frameworks, on a simulator. It took around 120ms on the background thread. I also wanted to test a release build on a real device, but I had trouble with the signing certificates. The SDK needs around 80 ms for the iOS-Swift sample project to swizzle on a simulator and around 20 ms on an iPhone 12.

Added 1000 ViewControllers and 10k classes generated with generate-classes.sh and to iOS-Swift and profiled iOS-Swift.

📝 Checklist

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

🔮 Next steps

[codecov-commenter]

Codecov Report

Merging #1361 (ecf222a) into master (74d66ff) will decrease coverage by 0.01%.
The diff coverage is 91.42%.

@@            Coverage Diff             @@
##           master    #1361      +/-   ##
==========================================
- Coverage   95.41%   95.40%   -0.02%     
==========================================
  Files         152      153       +1     
  Lines        5479     5500      +21     
==========================================
+ Hits         5228     5247      +19     
- Misses        251      253       +2     

Impacted Files	Coverage Δ
Sources/Sentry/SentrySubClassFinder.m	88.23% <88.23%> (ø)
Sources/Sentry/SentryUIViewControllerSwizziling.m	68.49% <93.33%> (+2.29%)	⬆️
...rces/Sentry/SentryPerformanceTrackingIntegration.m	100.00% <100.00%> (ø)
Sources/Sentry/SentryOptions.m	98.70% <0.00%> (-0.65%)	⬇️

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[brustolin]

Good solution!