Implement drag from free space also for QtQuickControls

Use window manager to handle window move when dragging from free space
also with QtQuickControls.

Registering QQuickItems is hacky, because there is no Style::polish
for QtQuickControls, so those items are now registered from ::isQtQuickControl.

Adaptation of the same patch from Breeze.

Differential Revision: https://phabricator.kde.org/D3638