Issue #21741: Update 147 test modules to use test discovery.

I have compared output between pre- and post-patch runs of these tests
to make sure there's nothing missing and nothing broken, on both
Windows and Linux.  The only differences I found were actually tests
that were previously *not* run.
diff --git a/Lib/test/test_pep292.py b/Lib/test/test_pep292.py
index fd5256c..1e5e227 100644
--- a/Lib/test/test_pep292.py
+++ b/Lib/test/test_pep292.py
@@ -244,11 +244,5 @@
                          'tim likes to eat a bag of ham worth $100')
 
 
-def test_main():
-    from test import support
-    test_classes = [TestTemplate,]
-    support.run_unittest(*test_classes)
-
-
 if __name__ == '__main__':
-    test_main()
+    unittest.main()