Additional $langcode argument added to FormatterInterface::view(), FormatterInterface::viewElements() and EntityReferenceFormatterBase::getEntitiesToView()

#2513094: ContentEntityBase::getTranslatedField and ContentEntityBase::__clone break field reference to parent entity introduced a regression when displaying translated references in untranslated fields.

To fix that, a small API change for field formatter plugins is necessary:

-  public function view(FieldItemListInterface $items);
+  public function view(FieldItemListInterface $items, $langcode = NULL);

-  public function viewElements(FieldItemListInterface $items);
+  public function viewElements(FieldItemListInterface $items, $langcode);

Most field formatters only override viewElements(), all they have to do is add the new argument and pass it along to any other method that needs it - typically the EntityReferenceFormatterBase;;getEntititiesToView() method used by formatters for entity_reference fields (and sub-field types like file or image reference fields), which also gets the additional $langcode parameter.

   /**
    * {@inheritdoc}
    */
-  public function viewElements(FieldItemListInterface $items) {
+  public function viewElements(FieldItemListInterface $items, $langcode) {
     $elements = array();
     $output_as_link = $this->getSetting('link');
 
-    foreach ($this->getEntitiesToView($items) as $delta => $entity) {
+    foreach ($this->getEntitiesToView($items, $langcode) as $delta => $entity) {
       $label = $entity->label();
       // If the link is to be displayed and the entity has a uri, display a
       // link.