OrderTotalSummary and OrderItemTable formatters can crash when used inside Views

The way OrderTotalSummary and OrderItemTable formatters build their renderable array is not compatible with inserting them into views.

Here are the steps to reproduce:

1. Make sure you have at least some orders already generated in your store
2. Create a new view on commerce order
3. Add "Total price" field to the view and specify "order total summary" as its formatter
4. Add "Order items" field to the view and specify "order item table" as its formatter
5. Observe nothing output in those 2 fields when the view is executed.

Both just do a simple (no-children) renderable array:
\Drupal\commerce_order\Plugin\Field\FieldFormatter\OrderTotalSummary::viewElements():

  public function viewElements(FieldItemListInterface $items, $langcode) {
    $order = $items->getEntity();
    return [
      '#theme' => 'commerce_order_total_summary',
      '#totals' => $this->orderTotalSummary->buildTotals($order),
    ];
  }

\Drupal\commerce_order\Plugin\Field\FieldFormatter\OrderItemTable::viewElements():

  public function viewElements(FieldItemListInterface $items, $langcode) {
    $order = $items->getEntity();
    return [
      '#type' => 'view',
      // @todo Allow the view to be configurable.
      '#name' => 'commerce_order_item_table',
      '#arguments' => [$order->id()],
      '#embed' => TRUE,
    ];
  }

Then the view runs the following code (in \Drupal\views\Plugin\views\field\EntityField::getItems()):

public function getItems(ResultRow $values) {
    if (!$this->displayHandler->useGroupBy()) {
      $build_list = $this->getEntityFieldRenderer()->render($values, $this);
    }
    else {
      // For grouped results we need to retrieve a massaged entity having
      // grouped field values to ensure that "grouped by" values, especially
      // those with multiple cardinality work properly. See
      // \Drupal\Tests\views\Kernel\QueryGroupByTest::testGroupByFieldWithCardinality.
      $display = [
        'type' => $this->options['type'],
        'settings' => $this->options['settings'],
        'label' => 'hidden',
      ];
      // Optional relationships may not provide an entity at all. So we can't
      // use createEntityForGroupBy() for those rows.
      if ($entity = $this->getEntity($values)) {
        $entity = $this->createEntityForGroupBy($entity, $values);
        // Some bundles might not have a specific field, in which case the faked
        // entity doesn't have it either.
        $build_list = isset($entity->{$this->definition['field_name']}) ? $entity->{$this->definition['field_name']}->view($display) : NULL;
      }
      else {
        $build_list = NULL;
      }
    }

  // ---------------------
  // --------------------- Here the $build_list is what the formatter has given us in its ::viewElements().
  // ---------------------

    if (!$build_list) {
      return [];
    }

    if ($this->options['field_api_classes']) {
      return [['rendered' => $this->renderer->render($build_list)]];
    }

  // ---------------------
  // --------------------- The part below is the problem: here we expect the $build_list to be
  // --------------------- indexed by deltas whereas the 2 formatters do not index them
  // --------------------- that way.
  // ---------------------

    // Render using the formatted data itself.
    $items = [];
    // Each item is extracted and rendered separately, the top-level formatter
    // render array itself is never rendered, so we extract its bubbleable
    // metadata and add it to each child individually.
    $bubbleable = BubbleableMetadata::createFromRenderArray($build_list);
    foreach (Element::children($build_list) as $delta) {
      BubbleableMetadata::createFromRenderArray($build_list[$delta])
        ->merge($bubbleable)
        ->applyTo($build_list[$delta]);
      $items[$delta] = [
        'rendered' => $build_list[$delta],
        // Add the raw field items (for use in tokens).
        'raw' => $build_list['#items'][$delta],
      ];
    }

  // ---------------------
  // --------------------- Thus down here we wind up with empty $items.
  // ---------------------

    return $items;
  }