Implement the tablet wayland protocol in kwin
Summary:
Uses the tablet classes introduced in kwayland.
Depends on D26858
Test Plan:
Scratched my tablet with a magic stick and it did things depending on the pressure.
https://youtu.be/GGx0TlNJlzs
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D26859