Issue #2157871 by tim.plunkett: Add ConfigStorageControllerInterface.

...lib/Drupal/Core/Config/Entity/ConfigStorageController.php

...l/Core/Config/Entity/ConfigStorageControllerInterface.php

...les/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php

...lock/tests/Drupal/block/Tests/BlockFormControllerTest.php

...s/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php

...ch/tests/Drupal/search/Tests/SearchPageRepositoryTest.php

...Drupal/shortcut/ShortcutSetStorageControllerInterface.php

...ules/system/lib/Drupal/system/Form/DateFormatFormBase.php

...s/system/lib/Drupal/system/PathBasedBreadcrumbBuilder.php

.../Drupal/taxonomy/VocabularyStorageControllerInterface.php

...s/user/lib/Drupal/user/RoleStorageControllerInterface.php