infra: allow worksteal for testing

setup.cfg

@@ -5,7 +5,7 @@ test=pytest
 xfail_strict = true
 # https://pytest-xdist.readthedocs.io/en/latest/known-limitations.html
 addopts =
-    --verbose -n logical --durations=0 --durations-min=1
+    --verbose -n logical --durations=0 --durations-min=1 --dist worksteal
 testpaths = test/unit_tests
 filterwarnings=
   # Issue #557 in `pytest-cov` (currently v4.x) has not moved for a while now,