Move the `Submit review` message to the top of review comments

Problem

The Finish review button opens up the popup letting us write a final message to the MR author, and that's super useful.

The only downside is that that message gets added at the end of all review messages, so the MR author gets to that often after having read, and potentially applied, the above suggestions.

I find myself using that "final message" to often let the author know that even if I left some suggestions, those are non-mandatory and the MR is good as it is, but if they want they could improve the code.

When I do this, 99% of the time, my teammates see the suggestions, apply them, then get at the end and notice that they were not "required" to apply those 😅

Proposal

Move the comment added by the Finish review button at the top of the review messages, so that the author can see that before seeing the other review comments 🙂

Caveats

I am aware of the sorting option for the discussions, and that would both be a workaround and an issue for the people sorting comments from newest to oldest, but this proposal would solve the issue for the vast majority (I think) of people 🙂

Do we have numbers about the sorting preference? Knowing how many users are sorting from newest to oldest, or the contrary, would help to decide if this proposal is worth it or not 🙂