swh_directory_walk/_one, our functions that list the contents of a directory, currently always join their results with the data from the content table.

When doing a one-off lookup, this is reasonable behavior as you often want the metadata associated with the contents in one go.

However, when doing analyses over a large amount of directories, the extra lookup incurs a lot of duplicate data that you could avoid. We should provide a "bare" version of those functions for those analyses.