Draft (review) notes can generate wrong suggestions

1. The user leaves a suggestion as a review note (the suggestion wasn't created in the DB yet)
2. Before finishing up and sending the review as comment, the file that received the "pre-suggestion" changes
3. Currently, when publishing the note (review note -> diff note) we use the note.original_position to fetch the diff content to generate the suggestion. That means that when a DraftNote becomes a DiffNote, the MR might have received updates, so the original_position might be pointing to an old revision, therefore in the transition time we might fetch old content to generate the suggestion, which might be confusing to the user.