Represent traffic islands as static objects

[tbleher]

Describe the feature

To properly simulate autonomous pedestrians using OSI (e.g. the OsiPedestrian model as developed as part of SETLevel), pedestrians need to know where traffic islands are. These can be represented in OpenDRIVE (see https://publications.pages.asam.net/standards/ASAM_OpenDRIVE/ASAM_OpenDRIVE_Specification/latest/specification/13_objects/13_14_object_examples.html#_trafficisland ) but there seems to be no way to represent them in OSI currently.

Describe the solution you would like

Traffic islands should be represented in OSI as stationary objects.

Suggestion: Add TYPE_TRAFFICISLAND to osi3::StationaryObject::Classification::Type

Describe alternatives you have considered

None

Describe the backwards compatibility

I believe there are no backward compatibility issues. As OpenDRIVE describes that vehicles should not drive over traffic islands, the concern regarding parking spots expressed in #798 should not apply here.