Issue #1987896 by tim.plunkett, kgoel, vijaycs85: Convert user_page() to a new style controller.

core/includes/install.core.inc

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

core/modules/user/lib/Drupal/user/Form/UserLoginForm.php

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

core/modules/user/lib/Drupal/user/RegisterFormController.php

core/modules/user/user.module

core/modules/user/user.pages.inc

core/modules/user/user.routing.yml