Add StatusCheckEvent to report errors and warnings in the staging error to the user

Problem/Motivation

Had some talks with @bnjmnm and @phenaproxima about this problem space

In #3284945: Install endpoints that leverage Package Manager + core APIs Project Browser is also firing the PreCreateEvent to check if the system meets all its requirements, but if another subscriber assumes a create is about to happen this could be a problem. In AutoUpdates we are using ReadinessCheckEvent but that is a AutoUpdates class and Project Browser just requires package_manager

In \Drupal\automatic_updates\Form\UpdateReady \Drupal\automatic_updates_extensions\Form\UpdateReady we call our StagedDatabaseUpdateValidator to warn the user about database updates. StagedDatabaseUpdateValidator is validator because it stops Cron updates

In #3293427: Display all projects that will be updated in Extensions confirmation form we will be displaying other dependencies that have been updated

Project browser also will need to display the messages about DB updates and new projects modules that have been updated or added.

Right now we have to build the logic into the form. But we could just fire StatusCheckEvent and display any warning. The forms themselve won't have to have any particular of what things to check.

Proposed resolution

Create StatusCheckEvent that will show warning and errors to the user.

It would be the module developers responsibility to show the warnings and error and to not allow the user to continue if there are errors.

then do #3304417: Deprecate ReadinessCheckEvent in favor of StatusCheckEvent in package manager