Wrong parent for assign_position and assign_orientation (should be physical object)

Arguably, the parent for assign_position and assign_orientation should be physical object and not movable object.

See https://publications.pages.asam.net/standards/ASAM_OpenSCENARIO/ASAM_OpenSCENARIO_DSL/latest/domain-model/actions.html#sec-actions_movableobjects-class-assign_position