Classic Editor: No way to submit for review

[ChaosExAnima]

There doesn't seem to be a way to submit a forked post for review in the classic editor.

Steps to reproduce:

1. As an author, create a post.
2. As an editor or admin, publish and create a fork.
3. As the author, edit the fork.

Expected result: Button to submit for review should be there. Actual result: No button is there.

Looking at the code, it seems that there's a check for whether the user can merge the post here: includes/Posts/PublishingButtons.php:193

Functions to determine if a user can view the fork but not publish should be introduced.