[3.13] gh-56596: Make IDLE key bindings work with Caps Lock on (GH-157709) #157739

Tk does not fold the case of letter keysyms, and Caps Lock changes it,

so bind each key sequence with the other case of its letters too.

(cherry picked from commit 0b18efdf12c56b7b1f2080aa26c419b0014bde77)

Co-authored-by: Serhiy Storchaka [email protected]
Co-authored-by: Terry Jan Reedy [email protected]

• Issue: gh-56596
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