bpo-33610: IDLE's code-context always shows current context immediately (GH-14821) (#14846)

Eliminate delay of up to 100ms and accompanying visual artifact.
Fix bug of never showing context when hide and show.
(cherry picked from commit e0a1f8fb5c60886dbddf1a3ccb5d47576bdd43e2)

Co-authored-by: Tal Einat <taleinat@gmail.com>
3 files changed