6 files declare their use of ConfigImporterEvent in Zircon Profile 8

BundleConfigImportValidate.php in core/lib/Drupal/Core/Entity/Event/BundleConfigImportValidate.php

Contains \Drupal\Core\Entity\Event\BundleConfigImportValidate.

ConfigImportSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php

Contains \Drupal\Core\EventSubscriber\ConfigImportSubscriber.

ConfigSnapshotSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ConfigSnapshotSubscriber.php

Contains \Drupal\Core\EventSubscriber\ConfigSnapshotSubscriber.

ConfigSubscriber.php in core/modules/config/src/ConfigSubscriber.php

Contains \Drupal\config\ConfigSubscriber.

EventSubscriber.php in core/modules/config/tests/config_import_test/src/EventSubscriber.php

Contains \Drupal\config_import_test\EventSubscriber.

SystemConfigSubscriber.php in core/modules/system/src/SystemConfigSubscriber.php

Contains \Drupal\system\SystemConfigSubscriber.