7 files declare their use of ContextProviderInterface in Drupal 9

CurrentLanguageContext.php in core/lib/Drupal/Core/Language/ContextProvider/CurrentLanguageContext.php

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

FakeViewModeContext.php in core/modules/layout_builder/tests/modules/layout_builder_fieldblock_test/src/ContextProvider/FakeViewModeContext.php

IHaveRuntimeContexts.php in core/modules/layout_builder/tests/modules/layout_builder_test/src/ContextProvider/IHaveRuntimeContexts.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

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