18 files declare their use of EntityContext in Drupal 9

ConditionTestDualUserTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Condition/ConditionTestDualUserTest.php

ContextDefinitionTest.php in core/tests/Drupal/KernelTests/Core/Plugin/ContextDefinitionTest.php

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

CurrentUserContext.php in core/modules/user/src/ContextProvider/CurrentUserContext.php

DefaultsSectionStorage.php in core/modules/layout_builder/src/Plugin/SectionStorage/DefaultsSectionStorage.php

DefaultsSectionStorageTest.php in core/modules/layout_builder/tests/src/Kernel/DefaultsSectionStorageTest.php

EntityContextDefinitionIsSatisfiedTest.php in core/tests/Drupal/Tests/Core/Plugin/Context/EntityContextDefinitionIsSatisfiedTest.php

EntityContextTypedDataTest.php in core/tests/Drupal/KernelTests/Core/Plugin/EntityContextTypedDataTest.php

LayoutBuilderEntityViewDisplay.php in core/modules/layout_builder/src/Entity/LayoutBuilderEntityViewDisplay.php

LayoutEntityHelperTrait.php in core/modules/layout_builder/src/LayoutEntityHelperTrait.php

LayoutEntityHelperTraitTest.php in core/modules/layout_builder/tests/src/Kernel/LayoutEntityHelperTraitTest.php

MultipleStaticContext.php in core/modules/block/tests/modules/block_test/src/ContextProvider/MultipleStaticContext.php

NodeRouteContext.php in core/modules/node/src/ContextProvider/NodeRouteContext.php

OptionalContextConditionTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Condition/OptionalContextConditionTest.php

OverridesSectionStorage.php in core/modules/layout_builder/src/Plugin/SectionStorage/OverridesSectionStorage.php

OverridesSectionStorageTest.php in core/modules/layout_builder/tests/src/Kernel/OverridesSectionStorageTest.php

QuickEditIntegration.php in core/modules/layout_builder/src/QuickEditIntegration.php

TermRouteContext.php in core/modules/taxonomy/src/ContextProvider/TermRouteContext.php