the goal is to rely on fontconfig for font directory resolution. it
doesn't seem like it would be appropritate to call to fontconfig funcs
from within the LibCore.
i'm not 100% confident that FontDatabase is the correct place.. seems
okay?
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.
