[core] Workaround erroneous urllib Windows proxy parsing

[coletdjnz]

Authored by: coletdjnz

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Backport from Network Rework.

Workaround for python/cpython#86793 for older Python versions.

See #4136 for explanation.

Note: this issue doesn't impact the current yt-dlp as https proxies are treated as http, but for when we add support for https proxies in the future this will be needed.
(In saying that we may want to add a warning if a user does pass a https proxy in the current state)

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Copilot Summary

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Summary

📦🛠️🔄

Patch urllib.request.getproxies to fix proxy detection on Windows. Create a new compat.urllib package that re-exports and patches the standard urllib module.

To fix proxy issues on Windows
We patch urllib with some hints
We use compat to re-export
The standard modules with some support
And update YoutubeDL with our prints

Walkthrough

• Create and use a custom version of getproxies to fix proxy detection issues on Windows (link, link, link)
  • Add a new module compat/urllib/request.py that re-exports and patches urllib.request.getproxies (link)
  • Import getproxies from compat/urllib/request.py instead of urllib.request in YoutubeDL.py (link)
  • Replace the call to urllib.request.getproxies with the local getproxies in YoutubeDL.py (link)
• Create a proxy module for urllib in compat/urllib/__init__.py to allow importing urllib from compat without breaking existing code (link)
  • Use a helper function passthrough_module to re-export all the symbols from urllib and make the local module act as a proxy for the standard module (link)