New hook_ENTITY_TYPE_form_mode_alter() hook added.

New hook hook_ENTITY_TYPE_form_mode_alter() has been added to allow modules implement form mode alter hook for only specific entity types.

For Usage, the module developers have to replace ENTITY_TYPE with node, user etc. Examples below:
Before

function example_entity_form_mode_alter(&$form_mode, \Drupal\Core\Entity\EntityInterface $entity) {
   if ($entity->getEntityTypeId() == 'node' && $entity->bundle() == 'article') {
    $form_mode = 'custom_article_form_mode';
  }
}

After

function example_node_form_mode_alter(string &$form_mode, \Drupal\Core\Entity\EntityInterface $entity) {
    if ($entity->bundle() == 'article') {
      $form_mode = 'custom_article_form_mode';
  }
}