8 files declare their use of ContextAwarePluginDefinitionInterface in Drupal 9

ContextAwarePluginBase.php in core/lib/Drupal/Component/Plugin/ContextAwarePluginBase.php

ContextAwarePluginBaseTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Context/ContextAwarePluginBaseTest.php

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

ContextAwarePluginTraitTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Context/ContextAwarePluginTraitTest.php

ContextHandler.php in core/lib/Drupal/Core/Plugin/Context/ContextHandler.php

ContextHandlerTest.php in core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php

Contains \Drupal\Tests\Core\Plugin\ContextHandlerTest.

LayoutDefinition.php in core/lib/Drupal/Core/Layout/LayoutDefinition.php

SectionStorageDefinition.php in core/modules/layout_builder/src/SectionStorage/SectionStorageDefinition.php