bpo-40275: Use new test.support helper submodules in tests (GH-21772)

diff --git a/Lib/test/libregrtest/refleak.py b/Lib/test/libregrtest/refleak.py
index 8d22123..77298d3 100644
--- a/Lib/test/libregrtest/refleak.py
+++ b/Lib/test/libregrtest/refleak.py
@@ -4,6 +4,8 @@
 import warnings
 from inspect import isabstract
 from test import support
+from test.support import os_helper
+
 try:
     from _abc import _get_dump
 except ImportError:
@@ -61,7 +63,7 @@
         return int_pool.setdefault(value, value)
 
     nwarmup, ntracked, fname = ns.huntrleaks
-    fname = os.path.join(support.SAVEDCWD, fname)
+    fname = os.path.join(os_helper.SAVEDCWD, fname)
     repcount = nwarmup + ntracked
 
     # Pre-allocate to ensure that the loop doesn't allocate anything new
@@ -71,7 +73,7 @@
     fd_deltas = [0] * repcount
     getallocatedblocks = sys.getallocatedblocks
     gettotalrefcount = sys.gettotalrefcount
-    fd_count = support.fd_count
+    fd_count = os_helper.fd_count
 
     # initialize variables to make pyflakes quiet
     rc_before = alloc_before = fd_before = 0
diff --git a/Lib/test/libregrtest/win_utils.py b/Lib/test/libregrtest/win_utils.py
index 028c011..a1cc220 100644
--- a/Lib/test/libregrtest/win_utils.py
+++ b/Lib/test/libregrtest/win_utils.py
@@ -5,7 +5,7 @@
 import subprocess
 import uuid
 import winreg
-from test import support
+from test.support import os_helper
 from test.libregrtest.utils import print_warning
 
 
@@ -69,7 +69,9 @@
         # Spawn off the load monitor
         counter_name = self._get_counter_name()
         command = ['typeperf', counter_name, '-si', str(SAMPLING_INTERVAL)]
-        self._popen = subprocess.Popen(' '.join(command), stdout=command_stdout, cwd=support.SAVEDCWD)
+        self._popen = subprocess.Popen(' '.join(command),
+                                       stdout=command_stdout,
+                                       cwd=os_helper.SAVEDCWD)
 
         # Close our copy of the write end of the pipe
         os.close(command_stdout)