[platforms/drm] Rotate screen if requested from KScreen

Summary:
This change hooks up the drm plane rotate with the rotation requests
from KScreen. Our requests support more than what KScreen exposes in the
UI, that is all the flipped variants. I do not really understand what
the flip means, so this is not implemented yet.

Furthermore this only implements the visual rotation and not the input
rotation. This means mouse movement and touch input is currently broken
on a rotated screen.

Please note that the hardware I used seems to not support the vertical
rotation. I'm not sure whether my code works. On my system it just
results in atomic commit errors and we need to go back to a previous
working state. This is not yet implemented. I need to test the vertical
rotation on my notebook, which should (in theory) support it.

Reviewers: #kwin, #plasma, subdiff, sebas

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D8594