[Defect]: modelCard misisng `properties` in XML & ProtoBuff

[jkowalleck]

Describe the defect

CycloneDX 1.5 introduced model cards.

these model cards may have properties in JSON - https://cyclonedx.org/docs/1.5/json/#components_items_modelCard_properties

The bug:

• these model cards are missing the properties in XML - https://cyclonedx.org/docs/1.5/xml/#type_modelCardType
• these model cards are missing the properties in ProtoBuff -
  https://cyclonedx.org/docs/1.5/proto/#cyclonedx.v1_5.ModelCard

This bug exists since v1.5
This bug exists in v1.7 still