chore: rework single python tests (#1835)

* chore: rework single python tests

* chore(tests): limit number of builds in test_abi3

* chore(tests): limit number of builds in test_before_all

* apply review suggestion

use `os.path.samefile` rather than comparing `os.stat` directly.

test/test_build_frontend_args.py

@@ -16,10 +16,8 @@ def test_build_frontend_args(tmp_path, capfd, frontend_name):
     with pytest.raises(subprocess.CalledProcessError):
         utils.cibuildwheel_run(
             project_dir,
-            add_env={
-                "CIBW_BUILD": "cp311-*",
-                "CIBW_BUILD_FRONTEND": f"{frontend_name}; args: -h",
-            },
+            add_env={"CIBW_BUILD_FRONTEND": f"{frontend_name}; args: -h"},
+            single_python=True,
         )
 
     captured = capfd.readouterr()