BE - update models and related code to use NAICS fields in AlternateName

[argush3]

In the new data model, NAICS fields should be moved from legal_entities table to alternate_names

TODOs

• do work in legal name branch
• Update appropriate model classes
  • add naics fields to AlternateName model
  • remove naics fields from legal_entity model
• Update any BE services that references NAICS fields in LegalEntities model to use AlternateNames model
• Add/update tests as appropriate