Ignore modifier mouse actions when the pointer is constrained
Summary:
If the pointer is constrained all mouse events should go to the window.
Also our Alt+click. To use Alt+click nevertheless one can just unconfine
the window.
CCBUG: 399375
Test Plan: Run the adjusted autotest before and after change
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D15982