Ensure that all Automatic Updates event subscribers only apply to Automatic Updates uses

Problem/Motivation

Now that we are working on #3245770: Create a service to composer install via package_manager from Automatic Updates it is important that the validators don't try to validate Automatic Updates logic when Project Browser or another modules are using package_manager

Proposed resolution

In the classes in `src/Validator` and `src/Event` and probably anywhere we are listening to StageEvent subclass events outside of package_manager we should check to see if the stage is an instance of \Drupal\automatic_updates\Updater

For instance we could do this

if (!$event->getStage() instanceof Updater) {
   return;
}

Remaining tasks

Do it