[3.11] gh-103737: IDLE - Remove unneeded .keys() for dict iteration (GH-110960) (#111027)

gh-103737: IDLE - Remove unneeded .keys() for dict iteration (GH-110960)

Add comments where .keys() is needed.
Leave debugger usages along because situation is unclear as indicated in expanded comment.
Most testing is manual.
(cherry picked from commit baefbb21d91db2d950706737a6ebee9b2eff5c2d)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>