gh-151678: Add tests for tkinter.simpledialog

[serhiy-storchaka]

Add tests for tkinter.simpledialog, covering SimpleDialog (the message and the buttons, the default button, go(), the <Return> and window-close bindings and the bell paths), the Dialog base class (the OK/Cancel button box and result), the query dialogs (validation, range checks, initial value, masking, and the askinteger/askfloat/askstring functions), and the default-root handling.

• Issue: Improve test coverage of tkinter #151678

[serhiy-storchaka]

It was split from PR #151848.

[miss-islington-app]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 3.15 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker f28ef858f5515d200319e9675d66f8f13afa5a0d 3.15

[bedevere-app]

GH-151859 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-151860 is a backport of this pull request to the 3.13 branch.

[miss-islington-app]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 3.15 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker f28ef858f5515d200319e9675d66f8f13afa5a0d 3.15

[miss-islington-app]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

[bedevere-app]

GH-151869 is a backport of this pull request to the 3.15 branch.