Move settings to an app (#17182)

.gitattributes

.gitignore

apps/provisioning_api/lib/AppInfo/Application.php

apps/provisioning_api/lib/Controller/UsersController.php

...provisioning_api/tests/Controller/UsersControllerTest.php

apps/settings/.babelrc.js

apps/settings/.editorconfig

apps/settings/.gitignore

apps/settings/.l10nignore

apps/settings/appinfo/info.xml

apps/settings/appinfo/routes.php

apps/settings/composer/autoload.php

apps/settings/composer/composer.json

apps/settings/composer/composer/ClassLoader.php

apps/settings/composer/composer/LICENSE

apps/settings/composer/composer/autoload_classmap.php

apps/settings/composer/composer/autoload_namespaces.php

apps/settings/composer/composer/autoload_psr4.php

apps/settings/composer/composer/autoload_real.php

apps/settings/composer/composer/autoload_static.php