bpo-4630: Add cursor no-blink option for IDLE (GH-16960)


This immediately toggles shell, editor, and output windows, but does not affect other input widgets.
(cherry picked from commit 9c2844927d15b2d3e21b28d62249dead02b5b597)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>
7 files changed