When the cursor is on the top or bottom line of the edit window, and
an <Up> or <Down> pushes the cursor offscreen, then use edit_scroll()
to bring it back into view, instead of using edit_redraw(), because
the latter would redraw *every row* on the screen, which is a waste
of time.

This addresses https://savannah.gnu.org/bugs/?53562

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Reported-by: Devin Hussey <husseydevin@gmail.com>