Issue #2027115 by dawehner, tim.plunkett: Allow views to override existing routing items.

core/lib/Drupal/Core/EventSubscriber/AccessSubscriber.php

core/lib/Drupal/Core/Routing/RouteCompiler.php

.../rest/lib/Drupal/rest/Plugin/views/display/RestExport.php

...odules/rest/tests/Drupal/rest/Tests/CollectRoutesTest.php

core/modules/user/lib/Drupal/user/Controller/UserAdmin.php

core/modules/user/user.admin.inc

core/modules/user/user.local_actions.yml

core/modules/user/user.module

core/modules/user/user.routing.yml

...iews/lib/Drupal/views/EventSubscriber/RouteSubscriber.php

...pal/views/Plugin/views/display/DisplayRouterInterface.php

.../lib/Drupal/views/Plugin/views/display/PathPluginBase.php

...s/views/lib/Drupal/views/Tests/Plugin/DisplayPageTest.php

...rupal/views/Tests/EventSubscriber/RouteSubscriberTest.php

.../Drupal/views/Tests/Plugin/display/PathPluginBaseTest.php

core/modules/views/views.module

core/modules/views/views.services.yml

...ui/tests/Drupal/views_ui/Tests/ViewListControllerTest.php