Issue #2237963 by Wim Leers: Remove dead menu system code: menu_get_active_trail() and friends.

core/includes/menu.inc

core/lib/Drupal/Core/Controller/ExceptionController.php

core/modules/menu_link/lib/Drupal/menu_link/MenuTree.php

...ules/menu_link/lib/Drupal/menu_link/MenuTreeInterface.php

...st/lib/Drupal/menu_test/Controller/MenuTestController.php

...rupal/menu_test/EventSubscriber/ActiveTrailSubscriber.php

...l/menu_test/EventSubscriber/ActiveTrailTestSubscriber.php

...s/system/tests/modules/menu_test/menu_test.menu_links.yml

core/modules/system/tests/modules/menu_test/menu_test.module

...ules/system/tests/modules/menu_test/menu_test.routing.yml

...les/system/tests/modules/menu_test/menu_test.services.yml