Windows: Respect integrated GPU preference in Windows Settings

[alvinhochun]

Tested locally with Vulkan.

Fixes #81870
Related to #58430

[alvinhochun]

Using Sysinternals Process Monitor I can observe that opengl32.dll reads the same registry key as this PR. It also reads the value DirectXUserGlobalSettings, however setting it manually doesn't seem to affect the GPU selection when using gl_compatibilty. So I'd wager this is good enough at least for when running as non-packaged desktop app.

However, I neglected that Windows Settings also allows selecting the preference for a packaged app, and the current change doesn't handle this case. It is slightly more annoying to test but implementation should be trivial (using GetCurrentPackageFamilyName GetCurrentApplicationUserModelId).

[alvinhochun]

Windows Settings also allows selecting the preference for a packaged app

This is now implemented, and I've verified that it works by hijacking another packaged app.

[bruvzg]

Reg. key name size is limited to 16K chars, I wounder what would happen if you try to set GPU preferences for app with longer path (will it truncate it or won't set it at all).

Probably not relevant in practice, Godot won't handle long paths without #91902, and CreateProcess can't handle long current directory paths, so it's unlikely will ever be over 260.

[alvinhochun]

Interesting point to consider. Though things are really whacky even when I make the Godot exe path just 256 chars -- it crashes when using the NVIDIA GPU and explorer.exe; even if I set it to use the Intel GPU (OpenGL selection is handled by the system) it still crashed explorer.exe (though it did run the project manager).

I think I am comfortable with leaving the code like this. It is obviously not a supported scenario (unless MS decides to raise the limit of the value name, which I doubt would ever happen) and RegOpenKeyExW should just return an error and the function returns false.

[akien-mga]

Thanks!