This trait is used to create parent nodes while walking
directories/trees. You need to implement it for your type (it is
already implemented for PathBuf).
Same API as file_path_types_iter but can yield sorted output
(and in that case reports all file system errors directly from the
call, items then always being Ok).
Descends into subdirs. You’ll want to use PathBuf for P unless
you have a need to store additional data in the parent nodes. When
sorted == true, sorts every directory level individually,
yielding sorted output at only the memory cost of the largest
directory.