Deprecate ReadinessCheckEvent in favor of StatusCheckEvent in package manager

Problem/Motivation

I talked to @bnjmnm who was working on #3284945: Install endpoints that leverage Package Manager + core APIs for Project Browser

To check if Composer installs would work here was doing
$pre_create_event = $this->eventDispatcher->dispatch(new PreCreateEvent($this->stage));
which will work but if any subscriber listens to this performs operations that should only happen when a install starts this could be a problem.

He can't use ReadinessChecks here because that is only in Automatic Updates

Proposed resolution

#3304367: Add StatusCheckEvent to report errors and warnings in the staging error to the user then

1. Deprecate ReadinessCheck and make all our ReadinessCheckEvent listeners listen to StatusCheck
2. in all the places we are firing ReadinessCheckEvent also fire StatusCheckEvent
3. Remove Drupal\automatic_updates\Validator\PackageManagerReadinessCheck and all the service definitions that use it.
4. Determine if we can also remove \Drupal\package_manager\Validator\PreOperationStageValidatorInterface