Part 3 of 3, continuing PR #7689. This covers 14 idlelib modules and their tests,
rpc to zoomheight except for run (already done) and tooltip (being done separately).
This follows the previous patch that changed idlelib file names.
Class names that matched old module names are not changed.
Change idlelib imports in turtledemo.__main__.
Exception: config-extensions.def. Previously, extension section
names, file names, and class names had to match. Changing section
names would create cross-version conflicts in config-extensions.cfg
(user customizations). Instead map old names to new file names
at point of import in editor.EditorWindow.load_extension.
Patch extensively tested with test_idle, idle_test.htest.py, a custom
import-all test, running IDLE in a console to catch messages,
and testing each menu item. Based on a patch by Al Sweigart.
replacing warnings.formatwarnings and to reverse replacement of
warnings.showwarnings when import is complete and when main function exits.
Add test_warning.py. Vinay Sajip provided capture_warnings function.