feat: Set entity type name in osi gt

At the moment the model_reference attribute in OSI GT is used for both, the 3d model asset file reference and the entity type name (for vehicles i.e. the model like "G12"). This PR separates the two usages into two attributes.

• update MantleAPI
• Set the new "type name" entity attribute in the OSI GT as source_reference.identifier[2]
• refactor FillSourceReference() for better maintenance

Related MR: openscenario1_engine!261 (merged)