6 files declare their use of CategorizingPluginManagerInterface

ActionManager.php in core/lib/Drupal/Core/Action/ActionManager.php
BlockManagerInterface.php in core/lib/Drupal/Core/Block/BlockManagerInterface.php
CategorizingPluginManagerTraitTest.php in core/tests/Drupal/Tests/Core/Plugin/CategorizingPluginManagerTraitTest.php
Contains \Drupal\Tests\Core\Plugin\CategorizingPluginManagerTraitTest.
ConditionManager.php in core/lib/Drupal/Core/Condition/ConditionManager.php
FieldTypePluginManagerInterface.php in core/lib/Drupal/Core/Field/FieldTypePluginManagerInterface.php
LayoutPluginManagerInterface.php in core/lib/Drupal/Core/Layout/LayoutPluginManagerInterface.php

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