gh-90473: Skip and document more failing tests on WASI (GH-93436)

- Mark more ``umask()`` cases
- ``dup()`` is not supported
- ``/dev/null`` is not available
- document missing features
- mark more modules as not available
(cherry picked from commit 069c96f84ccd302436be180c8628289cc0efa977)

Co-authored-by: Christian Heimes <christian@python.org>