pythonGH-103247: bypass the import cache on the _require_loader helper

This is not a fix for the importlib test monkeypatching leakage but it's
something that we probably should be doing anyway.

Signed-off-by: Filipe Laíns <lains@riseup.net>

Lib/test/test_import/__init__.py

@@ -24,6 +24,7 @@
 from unittest import mock
 import _testinternalcapi
 
+from test.support import import_helper
 from test.support import os_helper
 from test.support import (
     STDLIB_DIR, swap_attr, swap_item, cpython_only, is_emscripten,
@@ -57,7 +58,7 @@
 
 def _require_loader(module, loader, skip):
     if isinstance(module, str):
-        module = __import__(module)
+        module = import_helper.import_fresh_module(module)
 
     MODULE_KINDS = {
         BuiltinImporter: 'built-in',