Test code should properly handle unicode strings on Windows

[martinweismann]

inline std::vector<Lib3MF_uint8> ReadFileIntoBuffer(std::string sFileName)
inline void WriteBufferToFile(std::vector<Lib3MF_uint8> const & buffer, std::string sFileName)
see

lib3mf/Tests/CPP_Bindings/Include/UnitTest_Utilities.h

Line 79 in 30d5c2e

inline std::vector<Lib3MF_uint8> ReadFileIntoBuffer(std::string sFileName)

lib3mf/Tests/CPP_Bindings/Include/UnitTest_Utilities.h

Line 91 in 30d5c2e

inline void WriteBufferToFile(std::vector<Lib3MF_uint8> const & buffer, std::string sFileName)

both assume the input strings to be UTF-8. However, they only run properly on Linux, if the string is outside the ASCII-range.
We need to add proper platform independent handling, e.g. like in

lib3mf/Source/Common/Platform/NMR_ImportStream_Native.cpp

Line 51 in 30d5c2e

m_Stream.open(sFileName.c_str(), std::ios::in | std::ios::binary);