typing: set disallow_any_generics

This prevents referring to a generic type without filling in its generic
type parameters.

The FixtureDef typing might need some more refining in the future.

src/_pytest/setupplan.py

@@ -22,7 +22,7 @@ def pytest_addoption(parser: Parser) -> None:
 
 @pytest.hookimpl(tryfirst=True)
 def pytest_fixture_setup(
-    fixturedef: FixtureDef, request: SubRequest
+    fixturedef: FixtureDef[object], request: SubRequest
 ) -> Optional[object]:
     # Will return a dummy fixture if the setuponly option is provided.
     if request.config.option.setupplan: