[wayland] Confine pointer to screen geometry

Summary:
If the new pointer position is "off screen", PointerInputRedirection
just ignores that new position. So, pointer remains on its previous
position. In some particular cases, like reaching default panel, it
degrades desktop experience because one have to slowly move pointer in
order to reach what he/she wants.

This change addresses that problem by confining the new pointer position
to screen geometry.

BUG: 374867
FIXED-IN: 5.13.4

Test Plan: Ran tests

Reviewers: KWin, graesslin

Reviewed By: KWin, graesslin

Subscribers: kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D14036