Fonts on Windows are stored only in %WINDIR%\Fonts and
%LOCALAPPDATA%\Microsoft\Windows\Fonts, see https://stackoverflow.com/a/67078786
And system_data_directories() is not implemented on Windows yet.
And move canonicalized_path() to a static method on LexicalPath.
This is to make it clear that FileSystemPath/canonicalized_path() only
perform *lexical* canonicalization.