bpo-40275: Use new test.support helper submodules in tests (GH-21151)

Use new test.support helper submodules in tests:

* distutils tests
* test_buffer
* test_compile
* test_filecmp
* test_fileinput
* test_readline
* test_smtpnet
* test_structmembers
* test_tools
diff --git a/Lib/test/test_smtpnet.py b/Lib/test/test_smtpnet.py
index 74a00a9..72f51cd 100644
--- a/Lib/test/test_smtpnet.py
+++ b/Lib/test/test_smtpnet.py
@@ -1,10 +1,11 @@
 import unittest
 from test import support
+from test.support import import_helper
 from test.support import socket_helper
 import smtplib
 import socket
 
-ssl = support.import_module("ssl")
+ssl = import_helper.import_module("ssl")
 
 support.requires("network")