[Feedback] Summarize proposed changes in a merge request
Description
This issue is for providing feedback on the summarize merge request changes experiment that's available for merge requests.
Summaries in merge requests are now generated automatically after a commit and can be viewed in the following places:
| To-Do list |
 - Available when someone requests a review from you
|
| Email notifications |
 - Available when someone requests a review from you
|
| Merge request sidebar |
 Available on the MR page, on the top right action menu (kebab menu icon)
|
Previously, the feature was enabled via a /summarize_diff quick action, but this will be deprecated and removed in the future.