|field_value removes attached libraries from $build

Problem/Motivation

If there are libraries attached on $build then |field_value removes them.

For example, with photoswipe formatter active on an image field, using
{{ content.field_image|field_value }}
removes the photoswipe library from the render array, as it's placed on the first level.

  /**
   * Twig filter callback: Only return a field's value(s).
   *
   * @param array|null $build
   *   Render array of a field.
   *
   * @return array
   *   Array of render array(s) of field value(s). If $build is not the render
   *   array of a field, NULL is returned.
   */
  public function getFieldValue($build) {

    if (!$this->isFieldRenderArray($build)) {
      return NULL;
    }

    $elements = Element::children($build);
    if (empty($elements)) {
      return NULL;
    }

    $items = [];
    foreach ($elements as $delta) {
      $items[$delta] = $build[$delta];
    }

    return $items;
  }

https://git.drupalcode.org/project/twig_field_value/-/blob/8.x-1.x/src/T...

Steps to reproduce

We ran into it here: #3392968: $this->photoswipeAssetManager->attach() conflicts with twig_field_value "|field_value"

But I think it happens whenever something like

$build['#attached'][...]

exists.

Proposed resolution

Discuss if this is expected and acceptable or a bug
Find a way to keep the attached libraries, for example by moving them to a child element?

Remaining tasks

User interface changes

API changes

Data model changes