bpo-33855: More edits and new minimal tests for IDLE (GH-7761)

Part 2 of 3.  Continues PR #7689, changeset ee5ef30.
Edit and add tests for 18 modules, help_about to replace and run.
diff --git a/Lib/idlelib/percolator.py b/Lib/idlelib/percolator.py
index d18daf0..db70304 100644
--- a/Lib/idlelib/percolator.py
+++ b/Lib/idlelib/percolator.py
@@ -96,9 +96,8 @@
     cb2.pack()
 
 if __name__ == "__main__":
-    import unittest
-    unittest.main('idlelib.idle_test.test_percolator', verbosity=2,
-                  exit=False)
+    from unittest import main
+    main('idlelib.idle_test.test_percolator', verbosity=2, exit=False)
 
     from idlelib.idle_test.htest import run
     run(_percolator)