Issue #3347760: \Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem::fieldSettingsForm access a field config entity from form state, limiting its use to field UI
requested to merge issue/drupal-3347760:3347760-drupalcorefieldpluginfieldfieldtypeentityreferenceitemfieldsettingsform-access-a into 10.1.x