Since that's the idiomatic way to use this module

I also renamed the arguments to match what the keyword argument is
called. It doesn't matter too much for these specific tests, but for the
tests I'm about to add, it makes things a lot easier to get an overview
of.

Oh, and a test failure :O

I went through https://docs.python.org/3.10/library/os.html in order,
and added all the functions that works on paths.

`lstat` and `statvfs` were already modeled, but did not have any tests.

…ystemAccess

These operate on file descriptors, and not on paths. file descriptors
doesn't fit into the rest of our modeling, so I would rather remove them
than to make it look like it's properly handled.

I also did not include any of the functions that work on file
descriptors when looking through all of `os`. So this keeps everything
consistent at least ;)

I think it's more readable to have only one to cover all of these
changes, even though they came in through different PRs.