devel/py-pytest-xdist: Update to 3.3.1

• Introduce default PSUTIL and SETPROCTITLE options to reflect the settings as noted in "pyproject.toml".

• Switch to the PEP517 build framework.

• Update test suite and use USE_PYTHON=pytest to simplify the Makefile.

• Errors like this one [1] should be remedied with this update:

[...]
INTERNALERROR> File "/usr/local/lib/python3.9/site-packages/xdist/scheduler/each.py", line 1, in <module>
INTERNALERROR> from py.log import Producer
INTERNALERROR> ModuleNotFoundError: No module named 'py.log'; 'py' is not a package
[...]

This is because devel/py-py was removed from devel/py-pytest's
RUN_DEPENDS in 47177a522b37 as it's no longer a dependency since
py-pytest 7.2.0.

Changelog since 2.5.0:

https://github.com/pytest-dev/pytest-xdist/blob/v3.3.1/CHANGELOG.rst

PR: 274789
Reported by: QA run of textproc/py-ocrmypdf's test suite [1]
Approved by: bofh (maintainer)