Problem/Motivation
Split deprecation of drupal_schema_get_field_value() from #2124069: Convert schema.inc to a service
Proposed resolution
Add static \Drupal\Core\Entity\Sql\SqlContentEntityStorageSchema::castValue()
Remaining tasks
User interface changes
None
API changes
drupal_schema_get_field_value() deprecated in favour of \Drupal\Core\Entity\Sql\SqlContentEntityStorageSchema::castValue()