common: use native MultiByteToWideChar (#17738)
`std::codecvt_utf8<wchar_t>` is deprecated and produces warnings:
common/common.cpp:792:31: warning: 'codecvt_utf8<wchar_t>' is deprecated [-Wdeprecated-declarations]
792 | std::wstring_convert<std::codecvt_utf8<wchar_t>> converter;
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Signed-off-by: Adrien Gallouët <angt@huggingface.co>
