fields are deleted when reverting exported bundle entities

Attached patch fixes it for me + improves hook_{ENTITY_TYPE}_delete() to receiver a further parameter, delete. Not sure whether we should do so or better set something like $entity->is_revert, analogous to $entity->is_rebuild.

I've further improved the patch so we don't need an extra parameter in the deletion hook, but can just check whether the entity is in code during deletion. For that to work also in the case of feature-module-disabling I've added an extra check, so that the status is updated before the deletion hook is invoked.

Thus, modules can just rely on the entity-status to figure out when it is a revert or not.

-> Patch remains working + tests are green -> committed.