Issue #14599: Generalize a test for ImportError.path and add support

in Python/dynload_shlibs.c.

This should fix the remaining importlib test failure on Windows.
Support in AIX and HP-UX will be in a separate checkin.

Lib/test/test_import.py

@@ -337,28 +337,6 @@ class ImportTests(unittest.TestCase):
             del sys.path[0]
             remove_files(TESTFN)
 
-    @unittest.skipUnless(sys.platform == "win32", "Windows-specific")
-    def test_extension_import_fail(self):
-        # Issue 1559549 added `name` and `path` attributes to ImportError
-        # in order to provide better detail. Issue 10854 implemented those
-        # attributes on import failures of extensions on Windows.
-        debug = True if sys.executable[-6:] == "_d.exe" else False
-        pkg_name = "extension"
-        pkg_file = pkg_name + "{}".format("_d.pyd" if debug else ".pyd")
-        with open(pkg_file, "w"): pass
-        importlib.invalidate_caches()
-        try:
-            with self.assertRaises(ImportError) as err:
-                import extension
-            self.assertEqual(err.exception.name, pkg_name)
-            # The path we get back has the dot-slash, e.g., ".\\extension.pyd"
-            self.assertIsNotNone(err.exception.path,
-                'unexpected None for ImportError.path: '
-                '{!r}'.format(err.exception))
-            self.assertEqual(os.path.relpath(err.exception.path), pkg_file)
-        finally:
-            unlink(pkg_file)
-
 
 class PycRewritingTests(unittest.TestCase):
     # Test that the `co_filename` attribute on code objects always points