Remove concept of resolution dependent cursors

Summary:
It's not a concept that makes sense with proper scaling.

Cursor should be the big if you chose a big size, small if you choose a small size,
regardless of what output it happens to be on.

Test Plan:
Set size to 0
Ran kwin
Cursor size was fine

Reviewers: #kwin, graesslin

Reviewed By: #kwin, graesslin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D13607