Added finish review dropdown

What does this MR do and why?

Adds a finish review dropdown to the merge request reviews bar that allows users to add a comment when submitting a review.

Screenshots or screen recordings

How to set up and validate locally

Enable mr_review_submit_comment

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #244044 (closed)