Extend GeoPosition z coordinate calculation to cover cases of overlapping roads

In !234 (merged) the calculation of the z coordinate of a GeoPosition is fixed for most cases to use the height of the road surface instead of z=0. In specific cases at positions where roads are overlapping, the height of the road surface is ambiguous. This problem has been addressed in the latest OSC XML 1.3 standard with the attribute "verticalRoadSelection" to resolve the ambiguity: https://publications.pages.asam.net/standards/ASAM_OpenSCENARIO/ASAM_OpenSCENARIO_XML/latest/generated/content/GeoPosition.html

The default value of the attribute is 0, which means the top-most road is used. This is what is currently implemented in OSC1 engine. With this issue the height calculation shall be extended to use the new "verticalRoadSelection" attribute and cover also these use-cases.