Clean up todo in InlineBlockEntityOperations::handleEntityDelete() and use isLayoutCompatibleEntity()

Problem/Motivation

function foo_entity_delete(EntityInterface $entity) {
  $context = EntityContext::fromEntity($entity);
}

This will fail.

Introduced in #2791269: Allow saving pre-existing references to inaccessible items

Proposed resolution

If \Drupal\Core\Entity\Plugin\Validation\Constraint\ValidReferenceConstraintValidator::validate() can't load the unchanged entity from the DB (because it no longer exists), use the one we have

This ticket is now a clean up of a todo and update InlineBlockEntityOperations::handleEntityDelete() to use isLayoutCompatibleEntity()

Remaining tasks

N/A

User interface changes

N/A

API changes

N/A

Data model changes

N/A