gh-61842: Add hotkeys to resize IDLE's font

[ZackerySpytz]

The implementation is based on the font-resizing code in turtledemo.
Changing the font size with the hotkeys or the mouse wheel will not
modify the config setting.

https://bugs.python.org/issue17642

• Issue: IDLE add font resizing hot keys and wheel #61842

[terryjreedy]

#6665 for bpo-33397 defines a FontSizer class in textview.py and uses it for textviews and the help viewer. I intend for it to be used everywhere for key/wheel font resizing, especially including editor windows. So as is, this PR duplicates the work there and needs to be either rewritten or replaced.

You could help by reviewing that code and testing it on your system, and even better, copying the new textview into your branch (or a new one) and trying to use it for the editor.

Editor font resizing must also change the context window if present and the line number window if present. There should be a function that does that, but it might be hard-coded to use the general config values.

Changing configdialog font sizing is bpo-24776. My latest plan for that (msg334281) is to use the font sizer (or subclass) to change both the font sample and the number is a box.

[terryjreedy]

Whoops, hit wrong radiobutton.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[ZackerySpytz]

Thank you, @terryjreedy, for commenting on this PR. I would certainly like to help with adding this feature to IDLE. I will take a look at the other PR.