NodeViewBuilder no longer hardcodes langcode

NodeViewBuilder no longer hardcodes the display of the langcode field allowing for formatter configurations to take affect. Now will be possible to achieve formats like:

• Display name with native names
• Add flag icons for languages
• Display source language

Wrapper was kept for backwards compatibility.

User interface slightly changes because field-language-display will be set to its default configuration to match previously hardcoded values.

Now developers will be able to provide new formatters in the following way:

namespace Drupal\custom_formatter\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FieldItemInterface;
use Drupal\Core\Field\Plugin\Field\FieldFormatter\LanguageFormatter as BaseFormatter;

/**
 * Plugin implementation of the 'custom_formatter' formatter.
 *
 * @FieldFormatter(
 *   id = "language_custom_fomatter",
 *   label = @Translation("Language with flag"),
 *   field_types = {
 *     "language"
 *   }
 * )
 */
class LanguageCustomFormatter extends BaseFormatter {

  /**
   * {@inheritdoc}
   */
  protected function viewValue(FieldItemInterface $item) {
     // Code to display value.
  }
}