Filepath arguments have flaky support for non-ascii strings

[Trico-Everfire]

We discussed this on the discord, just wanted to make an issue abt it. The fix is to overload to std::filesystem::u8path as you stated.

Edit: the solution is to switch to using std::filesystem::path for all filesystem path arguments.

• bsppp
• fspp
• gamepp
• kvpp
• mdlpp
• sndpp
• sourcepp
• steampp
• toolpp
• vcryptpp
• vpkpp
• vtfpp