Issue #2112711 by tim.plunkett: Provide an easier mechanism for using drupal_get_form() directly.

core/includes/form.inc

...modules/action/lib/Drupal/action/ActionListController.php

core/modules/comment/comment.admin.inc

...comment/lib/Drupal/comment/Form/ConfirmDeleteMultiple.php

.../locale/lib/Drupal/locale/Controller/LocaleController.php

...modules/search/lib/Drupal/search/Form/SearchBlockForm.php

...les/search/lib/Drupal/search/Plugin/Block/SearchBlock.php

...odules/user/lib/Drupal/user/Controller/UserController.php

...ules/user/lib/Drupal/user/Plugin/Block/UserLoginBlock.php