Expose Layout Builder Sections to entity view displays (jsonapi/entity_view_display/entity_view_display)

Problem/Motivation

Layout builder Sections are removed jsonapi entity view displays.

This is follow up issue for Expose Layout Builder data to REST and JSON:API and Allow marking a config schema types to be marked as "internal" (to avoid exposing them via HTTP APIs).

Steps to reproduce

Open an entity view display "jsonapi/entity_view_display/entity_view_display". There is no "sections" under "third_party_settings/layout_builder"

The responsibe code is "Drupal\jsonapi\Normalizer\ResourceObjectNormalizer:196";

      // @todo Replace this workaround after https://www.drupal.org/node/3043245
      //   or remove the need for this in https://www.drupal.org/node/2942975.
      //   See \Drupal\layout_builder\Normalizer\LayoutEntityDisplayNormalizer.
      if ($context['resource_object']->getResourceType()->getDeserializationTargetClass() === 'Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay' && $context['resource_object']->getField('third_party_settings') === $field) {
        unset($field['layout_builder']['sections']);
      }

Proposed resolution

This patch remove this unset.