Use ruff instead of black, flake8, autoflake, pyupgrade

Config adapted from pytest.

testing/test_plugin.py

@@ -13,7 +13,7 @@ from xdist.workermanage import NodeManager
 def monkeypatch_3_cpus(monkeypatch: pytest.MonkeyPatch):
     """Make pytest-xdist believe the system has 3 CPUs."""
     # block import
-    monkeypatch.setitem(sys.modules, "psutil", None)  # type: ignore
+    monkeypatch.setitem(sys.modules, "psutil", None)
     monkeypatch.delattr(os, "sched_getaffinity", raising=False)
     monkeypatch.setattr(os, "cpu_count", lambda: 3)