Issue #2112759 by effulgentsia: Add ContentEntityInterface::hasField().

core/lib/Drupal/Core/Entity/ContentEntityBase.php

core/lib/Drupal/Core/Entity/ContentEntityInterface.php

core/lib/Drupal/Core/Entity/EntityRenderController.php

core/modules/comment/comment.module

...s/comment/lib/Drupal/comment/CommentStorageController.php

core/modules/path/path.module

...dules/system/tests/modules/entity_test/entity_test.module

core/modules/user/user.module