HaikuDepot : New Model Generation Script

Without functionally changing the generated
code, create a new mechanic for generation
in order that improvements can be later made.

Change-Id: If5b755ebd257658ab0e0a0045dd21a464b429c09
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7135
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>