Issue #3093955 by heddn, ressa: Send email alert to administrator after automatic update

automatic_updates.module

automatic_updates.services.yml

src/Controller/InPlaceUpdateController.php

src/Event/PostUpdateEvent.php

src/Event/UpdateEvents.php

src/EventSubscriber/PostUpdateSubscriber.php

src/Services/InPlaceUpdate.php

src/Services/Notify.php

src/Services/UpdateInterface.php

src/UpdateMetadata.php

templates/automatic-updates-post-update.html.twig

...omatic_updates/src/Controller/InPlaceUpdateController.php

tests/src/Functional/NotifyTest.php