Create a review submitted To-Do with summary

What does this MR do and why?

When a review has associated review summary generated by AI, show it in the To-Do item.

Calls the TodoService#review_submitted when a review summary is generated to create the To-Do.

This is behind automatically_summarize_mr_review feature flag.

Screenshots or screen recordings

How to set up and validate locally

1. Enable automatically_summarize_mr_review feature flag.
2. Follow https://docs.gitlab.com/ee/development/ai_features.html#test-ai-features-locally.
3. Submit a review on a MR not authored by you.
4. As the author of the MR, look at your TODOs and you should see a TODO item saying that a user reviewed your MR with the review summary.

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.

Related to #415732 (closed)