bpo-35099: Improve the doc about IDLE running user code. (GH-10350)


The section is renamed from "IDLE -- console differences".  It mostly
covers the implications of using custom sys.stdxxx objects.
(cherry picked from commit 5e7909032491cef17754a3208872655fe350e9be)

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