Issue #2107533 by tim.plunkett, dawehner, pwolanin, Berdir: Remove {menu_router}.

core/core.services.yml

core/includes/menu.inc

core/includes/path.inc

...b/Drupal/Core/EventSubscriber/RouterRebuildSubscriber.php

...b/Drupal/basic_auth/Authentication/Provider/BasicAuth.php

...ock/lib/Drupal/custom_block/Tests/CustomBlockTypeTest.php

core/modules/book/lib/Drupal/book/BookManager.php

core/modules/contact/contact.module

core/modules/content_translation/content_translation.module

.../content_translation/Tests/ContentTranslationTestBase.php

core/modules/menu/lib/Drupal/menu/Form/MenuDeleteForm.php

core/modules/menu/lib/Drupal/menu/MenuFormController.php

core/modules/menu/menu.install

...u_link/lib/Drupal/menu_link/MenuLinkStorageController.php

...ons/lib/Drupal/options/Tests/OptionsFieldUnitTestBase.php

.../modules/simpletest/lib/Drupal/simpletest/WebTestBase.php

...em/lib/Drupal/system/Tests/Menu/MenuRouterRebuildTest.php

...es/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php

...dules/system/lib/Drupal/system/Tests/Menu/RebuildTest.php

...es/system/lib/Drupal/system/Tests/Menu/TreeAccessTest.php