Consider replacing std::wstring_convert with appropriate alternative for Windows.

[ni4]

Description

• std::wstring_convert is deprecated as of C++17 (and latest Botan uses C++20)
• it has some memory leak for one kinda major implementation: https://github.com/microsoft/STL/blob/92508bed6387cbdae433fc86279bc446af6f1b1a/stl/inc/cvt/wstring#L33

See the discussion/details here: https://www.reddit.com/r/cpp/comments/es9gt1/since_stdwstring_convert_is_deprecated_what_is/