FakeInput: add support for pointer move with absolute coordinates

Summary: For remote desktop support, we need to move with the pointer using absolute positin.

Test Plan: I tested this with xdg-desktop-portal-kde and krfb and it worked.

Reviewers: davidedmundson, graesslin, zzag

Reviewed By: davidedmundson, zzag

Subscribers: graesslin, zzag, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D18114