Ensure file system is writeable

Problem/Motivation

The file system has to be writable to do the update

Proposed resolution

For general instructions see the parent issue: #3230045: [Meta] Create validation listeners

The subscriber should subscribe to events `\Drupal\automatic_updates\AutomaticUpdatesEvents::READINESS_CHECK` and `\Drupal\automatic_updates\AutomaticUpdatesEvents::PRE_START`
it should add a Error validation result if the file system is not writable.

actual check will be something like in 8.x-1.x https://git.drupalcode.org/project/automatic_updates/-/blob/8.x-1.x/src/...