Make debug geometry reflect physics engine state exactly

Currently, the debug geometry lives in the scene at the same level as the collision shape. This means that if there is a scene transformation that is not supported by the physics engine, the debug geometry will still show the effects of that transformation, e.g. if a non-uniform scale is applied to a sphere shape.

The solution is probably to make all debug models live at the top level, and apply transforms from PxRigidActor::getGlobalPose().