Issue #3432052 by catch: @group slow for more Kernel tests

...ckeditor5/tests/src/Kernel/CKEditor5PluginManagerTest.php

core/modules/ckeditor5/tests/src/Kernel/ValidatorsTest.php

...oderation/tests/src/Kernel/ContentModerationStateTest.php

core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php

.../modules/field/tests/src/Kernel/Number/NumberItemTest.php

.../media/tests/src/Kernel/MediaAccessControlHandlerTest.php

...rnel/Entity/EntityReferenceSelectionReferenceableTest.php

...al/KernelTests/Core/Config/SimpleConfigValidationTest.php

...rnelTests/Core/Entity/EntityViewDisplayValidationTest.php