cloud-compatible Path usage #1867

It should be easy to write metadata directly to a Path-like object supporting cloud storage, like from universal-pathlib. A few small tweaks are needed to allow this, like not directly creating a new Path inside recursive_check_paths. We may at some point want to change type annotations to reflect this support using https://github.com/barneygale/pathlib-abc, but for now we can just use the existing Path type annotations and rely on duck typing.