fix(kded): read rotated output size

Summary:
When adjusting positions on config read respect the rotation value on reading
in the output size.

BUG: 413627
CCBUG: 396354
FIXED-IN: 5.17.3

Test Plan: User tested it on a setup with one rotated output and two non-rotated outputs.

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: davidedmundson, gmassullo, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D25062