Issue #2834768 by woprrr, psiegel, DuneBL: Route alteration refactor

form_mode_manager.module

form_mode_manager.services.yml

...mples/config/install/node.type.node_form_mode_example.yml

src/Controller/FormModeManagerController.php

src/FormDisplayManager.php

src/FormModeManagerPermissions.php

src/ParamConverter/FormModeManagerConverter.php

src/Plugin/Derivative/FormModeManagerLocalAction.php

src/Plugin/Derivative/FormModeManagerLocalTasks.php

src/Routing/FormModeManagerRouteSubscriber.php