Confirm that all backends properly iterate over directories

[pjbull]

Most cloud services don't have a notion of a "directory." We try to add this back in within our logic by doing our own path splitting.

We should make sure that the pathlib methods (glob and iterdir) and our methods do the same thing of:

• Returning directories and/or files when iterating
• Returning the root or current directory when being asked to iter or not
• Sort order of the returned results (may not be possible/worth it since we use a generator)

[pjbull]

Here are the CPython tests for glob:
https://github.com/python/cpython/blob/022bc7572f061e1d1132a4db9d085b29707701e7/Lib/test/test_pathlib.py#L1542-L1665

[karolzlot]

For at least S3 it works differently than in-built Path: it includes also current folder.

It should be fixed.