9 files declare their use of DependentPluginInterface in Zircon Profile 8

ArgumentPluginBase.php in core/modules/views/src/Plugin/views/argument/ArgumentPluginBase.php

Contains \Drupal\views\Plugin\views\argument\ArgumentPluginBase.

Config.php in core/modules/migrate/src/Plugin/migrate/destination/Config.php

Contains \Drupal\migrate\Plugin\migrate\destination\Config.

DisplayPluginBase.php in core/modules/views/src/Plugin/views/display/DisplayPluginBase.php

Contains \Drupal\views\Plugin\views\display\DisplayPluginBase.

DrupalSqlBase.php in core/modules/migrate_drupal/src/Plugin/migrate/source/DrupalSqlBase.php

Contains \Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase.

EmptySource.php in core/modules/migrate_drupal/src/Plugin/migrate/source/EmptySource.php

Contains \Drupal\migrate_drupal\Plugin\migrate\source\EmptySource.

Entity.php in core/modules/migrate/src/Plugin/migrate/destination/Entity.php

Contains \Drupal\migrate\Plugin\migrate\destination\Entity.

PluginBase.php in core/modules/views/src/Plugin/views/PluginBase.php

Contains \Drupal\views\Plugin\views\PluginBase.

PluginDependencyTrait.php in core/lib/Drupal/Core/Plugin/PluginDependencyTrait.php

Contains \Drupal\Core\Plugin\PluginDependencyTrait.

PluginSettingsBase.php in core/lib/Drupal/Core/Field/PluginSettingsBase.php

Contains \Drupal\Core\Field\PluginSettingsBase.