Returns the field processor for a given field type.
string $field_type: The field type.
\Drupal\tmgmt_content\FieldProcessorInterface $field_processor The field processor for this field type.
protected function getFieldProcessor($field_type) {
$definition = \Drupal::service('plugin.manager.field.field_type')
->getDefinition($field_type);
return \Drupal::service('class_resolver')
->getInstanceFromDefinition($definition['tmgmt_field_processor']);
}