Pass bundle-specific field definition into formatter::isApplicable()

[@roderik] are you sure it is the base field definition?

The method Entity/EntityFieldManager::getFieldDefinitions is fetching bundle specific field definitions. (from \Drupal\custom_elements_ui\Form\EntityCustomElementsDisplayEditForm::getFieldDefinitions)

  /***
   * Allows all fields and not only whose display is configurable.
   *
   * @return \Drupal\Core\Field\FieldDefinitionInterface[]
   *   The array of field definitions
   */
  protected function getFieldDefinitions() {
    return $this->entityFieldManager->getFieldDefinitions($this->entity->getTargetEntityTypeId(), $this->entity->getTargetBundle());
  }

@useernamee thank you, you're right.

Some fields pass a BaseFieldDefinition class, but some fields pass a FieldConfig class.

(And all of these have a getSetting() that should contain whatever a specific formatter needs. I just needed to wade through some TypedData stuff and Plugin stuff, to be able to verify that my application code can work with this.)

So this issue is 'works as designed'.