feat: add support for SOCKS5 proxy

[JoshuaMoelans]

Fixes #1030

Todo

• Add SOCKS5 proxy option
• Handle transport when SOCKS5 proxy is given
  -> currently checked for MacOS using Curl transport
• also check for Linux transport
• Add Proxy integration tests
  -> using mitmproxy
• Add CI step to install mitmproxy
  -> replaced by adding it to requirements.txt
• Merge Crashpad PR
• Update changelog
• Update docs
  -> especially about socks5 being circumvented if proxy is unavailable on mac
  -> similar story on Windows with Autoproxy circumventing the proxy if a connection is possible
  -> ❗️ this only manifested in the capture test, NOT in the crash test -> ToDo: reason about why crashpad doesn't autoproxy?
  -> document which transports/platforms don't support it (e.g. winhttp)

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 82.43%. Comparing base (d431ab9) to head (37d075c).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1063      +/-   ##
==========================================
+ Coverage   82.38%   82.43%   +0.04%     
==========================================
  Files          53       53              
  Lines        7751     7760       +9     
  Branches     1216     1215       -1     
==========================================
+ Hits         6386     6397      +11     
  Misses       1253     1253              
+ Partials      112      110       -2     

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• Flaky Tests Detection - Detect and resolve failed and flaky tests

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 37d075c

[supervacuus]

This looks great, thanks! Just a few minor changes and questions.

[supervacuus]

Thanks! I know this was quite the odyssey, but the resulting integration tests alone are worth the pain ❤️.