fixtures: fix non-working package-scope parametrization reordering

The `.parent` was incorrectly removed in
a21fb87a90, but it was actually correct
(well, it assumes that Module.path.parent == Package.path, which I'm not
sure is always correct, but that's a different matter). Restore it.

Fix #12328.

testing/python/fixtures.py

@@ -4274,6 +4274,39 @@ class TestScopeOrdering:
         request = TopRequest(items[0], _ispytest=True)
         assert request.fixturenames == "s1 p1 m1 m2 c1 f2 f1".split()
 
+    def test_parametrized_package_scope_reordering(self, pytester: Pytester) -> None:
+        """A paramaterized package-scoped fixture correctly reorders items to
+        minimize setups & teardowns.
+
+        Regression test for #12328.
+        """
+        pytester.makepyfile(
+            __init__="",
+            conftest="""
+                import pytest
+                @pytest.fixture(scope="package", params=["a", "b"])
+                def fix(request):
+                    return request.param
+            """,
+            test_1="def test1(fix): pass",
+            test_2="def test2(fix): pass",
+        )
+
+        result = pytester.runpytest("--setup-plan")
+        assert result.ret == ExitCode.OK
+        result.stdout.fnmatch_lines(
+            [
+                "  SETUP    P fix['a']",
+                "        test_1.py::test1[a] (fixtures used: fix, request)",
+                "        test_2.py::test2[a] (fixtures used: fix, request)",
+                "  TEARDOWN P fix['a']",
+                "  SETUP    P fix['b']",
+                "        test_1.py::test1[b] (fixtures used: fix, request)",
+                "        test_2.py::test2[b] (fixtures used: fix, request)",
+                "  TEARDOWN P fix['b']",
+            ],
+        )
+
     def test_multiple_packages(self, pytester: Pytester) -> None:
         """Complex test involving multiple package fixtures. Make sure teardowns
         are executed in order.