bpo-40468: Split IDLE settings General tab (GH-26621)

Replace it with Windows tab for Shell and Editor options
and Shell/Ed for options exclusive to one of them.

Create room for more options and make dialog shorter,
to better fit small windows.
(cherry picked from commit 275d5f7957dbb56a6d5e1248addff210ee2e7270)

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