Fix GlobalTransform updates for entities with non-physics children

[Jondolf]

Objective

#380 significantly sped up transform propagation by reducing unnecessary work with physics entity ancestor markers. However, it also seems to have caused a severe bug: GlobalTransform is not updated for rigid bodies that have children that all are not physics entities.

The problem lies in propagate_transforms_physics, which only iterates through entities that are marked as ancestors of rigid bodies or colliders. Rigid bodies that have children but no physics entity descendants are just skipped.

Solution

In sync_simple_transforms_physics, don't only iterate through rigid bodies with no children, but also through rigid bodies that have children but are not ancestors of other physics entities.