Only emulate up/down key presses for mouse scrolls on alternate screen

Summary:
Konsole sends up/down key press events for mouse scrolls for apps that
aren't interested in mouse events, such as less. Only do this when the
terminal is using the alternate screen.

Now scrolling up/down will be translated to up/down key presses only
when the terminal is using the alternate screen but scrolling in a terminal
using the primary screen will only scroll using the scrollbar, now it does
not cycle through the shell history.
Now the behavior matches xterm and and gnome-terminal.

BUG: 355106
FIXED-IN: 18.04

Reviewers: hindenburg

Reviewed By: hindenburg

Subscribers: rkflx, ngraham, Konsole

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D11146