Refactor bundle fields when Drupal core supports code-defined bundle fields

As @paul121 noticed in #3192245: Storage is not created for fields created with hook_farm_entity_bundle_field_info until a new entity of that type is installed, the FarmFieldFactory class currently uses FieldDefinitionInterface for all type-hinting, which leads to IDEs complaining because the code references properties/methods that are present on BaseFieldDefinition classes, but not on the FieldDefinitionInterface interface.

Explanation (copied from that issue thread):

The reason I used FieldDefinitionInterface is because FarmFieldFactory actually has to produce two different output object classes: BaseFieldDefinition and BundleFieldDefinition. So by using FieldDefinitionInterface it covers both. I agree this isn't perfect, and the IDE type-hinting issue you mention is a side-effect of that. But it may be a necessary evil until (if) core adopts a unified field definition class for base and bundle fields.

I pushed a commit that adds some @todo comments linking back to this issue, for future reference.

the FarmFieldFactory class currently uses FieldDefinitionInterface for all type-hinting

This is no longer the case - see last commit of #3192245: Storage is not created for fields created with hook_farm_entity_bundle_field_info until a new entity of that type is installed. We changed to BaseFieldDefinition for parameter type hinting, which is correct because BundleFieldDefinition is a child class, so even though FarmFieldFactory can return either type, it can still use BaseFieldDefinition for all its type-hinting.

Generalizing this issue a bit... we made the Consumer fields in to BundleFieldDefinitions declared in hook_entity_base_field_info() (not hook_farm_entity_bundle_field_info()). These will also need to be refactored if/when core supports bundle fields.