This should solve several problems and remove the need for a rotation
order API. This does break the existing code though.

[ChangeLog] Node.rotation is now a quaternion, Node.eulerRotation a
vector3d of euler angles. Node.rotationOrder has been removed.

Fixes: QTBUG-77609
Change-Id: Ib1f4f3e173512cefb7f6863d2b431581e98587e2
Reviewed-by: Christian Strømme <christian.stromme@qt.io>