bpo-30993: IDLE - Improve configdialog font page and tests.  (#2818)

* Document causal event pathways in docstring.
* Simplify some attribute names.
* Rename test_bold_toggle_set_samples to make test_font_set fail.
* Fix test_font_set so not order dependent.
* Fix renamed test_indent_scale so it tests the widget.
3 files changed