Incorrect encoding used in embedded :/qt/etc/qt.conf resource

When generating the embedded :/qt/etc/qt.conf resource, the prefixPath is encoded using the local 8-bit encoding via QString::toLocal8Bit():

https://github.com/qtproject/pyside-pyside-setup/blob/dd79ee6d29b4a628aad61e24ae361ac6cab20ebf/sources/pyside6/libpyside/pyside.cpp#L878

However, the QSettings implementation in Qt6 assumes that the values are encoded as UTF-8.

Therefore, PYSIDE-972 is actually only fixed in PySide6 under Linux and macOS (where QString::toLocal8Bit() is equivalent to QString::toUtf8()), but the issue still persists on Windows. If the path contains a non-ASCII character, the paths returned by QLibraryInfo::path() end up mangled, which for example prevents discovery and loading of plugins.