Issue #1992428 by andypost: Convert Roles management to a Controller.

...b/Drupal/system/Tests/Upgrade/UserRoleUpgradePathTest.php

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

.../modules/user/lib/Drupal/user/Plugin/Core/Entity/Role.php

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

core/modules/user/user.admin.inc

core/modules/user/user.module

core/modules/user/user.routing.yml