[issue31001] IDLE: Add tests for configdialog highlight tab

[Terry J. Reedy]

New submission from Terry J. Reedy:

Pr2908 originally just sorted highlight methods together, but was extended to sort all methods together and relabeled for #31060.  (This actually simplified the diff.)  Pr2925, the 3.6 backport, appears on the replacement issue.

----------

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue31001>
_______________________________________