bpo-40275: Use new test.support helper submodules in tests (GH-21317)

diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 5969793..afc9555 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -15,6 +15,8 @@
 import unicodedata
 import unittest
 import warnings
+from test.support import import_helper
+from test.support import warnings_helper
 from test import support, string_tests
 from test.support.script_helper import assert_python_failure
 
@@ -504,7 +506,7 @@
         self.assertIs(text.replace(pattern, pattern), text)
 
     def test_bytes_comparison(self):
-        with support.check_warnings():
+        with warnings_helper.check_warnings():
             warnings.simplefilter('ignore', BytesWarning)
             self.assertEqual('abc' == b'abc', False)
             self.assertEqual('abc' != b'abc', True)
@@ -725,7 +727,7 @@
         import _testcapi
         u = '𝖀𝖓𝖎𝖈𝖔𝖉𝖊'
         self.assertTrue(u.isidentifier())
-        with support.check_warnings():
+        with warnings_helper.check_warnings():
             warnings.simplefilter('ignore', DeprecationWarning)
             self.assertTrue(_testcapi.unicode_legacy_string(u).isidentifier())
 
@@ -2507,7 +2509,7 @@
 
     # Test PyUnicode_FromFormat()
     def test_from_format(self):
-        support.import_module('ctypes')
+        import_helper.import_module('ctypes')
         from ctypes import (
             pythonapi, py_object, sizeof,
             c_int, c_long, c_longlong, c_ssize_t,
@@ -2748,7 +2750,7 @@
     @support.cpython_only
     def test_aswidechar(self):
         from _testcapi import unicode_aswidechar
-        support.import_module('ctypes')
+        import_helper.import_module('ctypes')
         from ctypes import c_wchar, sizeof
 
         wchar, size = unicode_aswidechar('abcdef', 2)
@@ -2786,7 +2788,7 @@
     @support.cpython_only
     def test_aswidecharstring(self):
         from _testcapi import unicode_aswidecharstring
-        support.import_module('ctypes')
+        import_helper.import_module('ctypes')
         from ctypes import c_wchar, sizeof
 
         wchar, size = unicode_aswidecharstring('abc')