[2.0]: Harmonize BOM metadata authorship with the party model

[taleodor]

Describe the feature

The 2.0 draft currently has two parallel representations of "who made this":

1. Components use the new party model — components[].parties[] with
   roles[] (manufacturer, author, supplier, …) and an
   organization / person / system / persona identity
   (cyclonedx-party-2.0.schema.json, introduced in Initial commit of the party model and test cases. #930).
2. BOM metadata still uses the 1.x discrete fields —
   metadata.manufacturer (organizationalEntity), metadata.authors[]
   (organizationalContact), and metadata.supplier
   (cyclonedx-metadata-2.0.schema.json).

Possible solutions

Replace metadata.manufacturer / metadata.authors / metadata.supplier
with metadata.parties[].