Fix an issue in our PyTest wrapper, that caused this recursion error:
```
File "shibokensupport/signature/loader.py", line 61, in feature_importedgc
File "shibokensupport/feature.py", line 137, in feature_importedgc
File "shibokensupport/feature.py", line 148, in _mod_uses_pysidegc
File "/usr/lib/python3.10/inspect.py", line 1147, in getsourcegc
lines, lnum = getsourcelines(object)gc
File "/usr/lib/python3.10/inspect.py", line 1129, in getsourcelinesgc
lines, lnum = findsource(object)gc
File "/usr/lib/python3.10/inspect.py", line 954, in findsourcegc
lines = linecache.getlines(file, module.__dict__)gc
File "/home/user/.cache/pypoetry/virtualenvs/dangerzone-hQU0mwlP-py3.10/lib/python3.10/site-packages/py/_vendored_packages/apipkg/__init__.py", line 177, in __dict__gc
self.__makeattr(name)gc
File "/home/user/.cache/pypoetry/virtualenvs/dangerzone-hQU0mwlP-py3.10/lib/python3.10/site-packages/py/_vendored_packages/apipkg/__init__.py", line 157, in __makeattrgc
result = importobj(modpath, attrname)gc
File "/home/user/.cache/pypoetry/virtualenvs/dangerzone-hQU0mwlP-py3.10/lib/python3.10/site-packages/py/_vendored_packages/apipkg/__init__.py", line 75, in importobjgc
module = __import__(modpath, None, None, ["__doc__"])gc
File "shibokensupport/signature/loader.py", line 54, in feature_importgc
RecursionError: maximum recursion depth exceededgc
```
This error seems to be related to
https://github.com/pytest-dev/pytest/issues/1794. By not importing
`pytest` in our test wrapper, and instead executing directly, we can
avoid it.
Note that this seems to be triggered only by Shiboken6, which is why we
hadn't previously encountered it.
Instability in the automated tests sometimes would sometimes fail when
running "podman images --format {{.ID}}". It turns out that in versions
prior to podman 4.3.0, podman volumes (stored in
~/.local/share/contaiers) would get corrupted when multiple tests were
run in parallel.
The current solution is to wrap the test command to run sequentially in
versions prior to the fix and in parallel for versions after that.
Fixes#217