`FileMangager.enumerator(at:)` stops enumerating after hitting path with more than 260 characters on Windows

[ahoppen]

When enumerating through a directory using FileManager.enumerator(at:) and one of the paths in that directory exceeds Window’s maximum path length of 260 characters, the enumerator silently stops. I’m not sure what I would expect but I think I would expect it to maybe skip the files that exceed the path length, not to stop enumeration altogether.

[jakepetroules]

Also, paths greater than 260 characters are allowed when long path support is enabled, and I think PathRelativePathTo has bugs which cause it to work improperly with long paths, so we should probably be using a different API.