Add subType to VehicleClassification in alignment with OpenSCENARIO 1.2

[adrianschultz]

Describe the feature

In OpenSCENARIO there is a VehicleCategory (comparable to VehicleClassification/Type see: https://www.asam.net/static_downloads/modelDocumentation/content/VehicleCategory.html) to describe a Vehicle. This will be extended with a VehicleType for Vehicle, with values "Ambulance", "Fire", "Police", "Road assistance vehicle".

To align the standards in that regard, the VehicleType could be added to VehicleClassification as SubType enum.

Describe the backwards compatibility

This should be fully backward compatible as it is only adding an optional enum to VehicleClassification .

[HendrikAmelunxen]

Output from a discussion during OIS-CCB meeting:
It would make sense to separate the classification of Fire, Police, Ambulance, etc. from the VehicleType. By this, combinations like police vehicles, police vans, police busses, fire semitrailers, fire trucks, etc. can be covered. Maybe this is also applicable for OSC?

[adrianschultz]

This was implemented in OpenSCENARIO and will most probably be part of the 1.2 release.

Therfore I propose to add something similar to VehicleClassification in OSI. Then we would have the possibility to set a osi3::MovingObject::VehicleClassification::Type and a osi3::MovingObject::VehicleClassification::VehicleRole like it was suggested in the CCB meeting.

[adrianschultz]

I added a PR (#613), which we can discuss in the group next week