Replace entities with entity types in TranscriptionEntity

https://redmine.teklia.com/issues/11004

Requires backend#1922 (closed)

• The TranscriptionEntity.entity property becomes TranscriptionEntity.type: EntityType
• The EntityLight and EntityMetas types are removed
• Token.entity becomes Token.type?: EntityType in src/helpers/entity.ts
• The search types in src/types/search.ts should use transcriptionentity_* fields instead of entity_*