Automatically perform Duo Code Review on each merge request
## Problem to Solve
Duo Code Review is a valuable part of the review process, but currently requires users to manually ask for reviews.
## Proposal
Projects should be able to configure Duo Code Review to automatically run on each MR.
1. We add a new setting for `Perform Duo Code Review on merge requests`
1. This setting will live in `/-/settings/merge_requests`.
2. ~~Under `Settings / General`, there will be a link to the above setting to help discoverability.~~
1. Decision to remove this link https://gitlab.com/gitlab-org/gitlab/-/merge_requests/188069#note_2455740483
4. See UX proposal/screenshot in https://gitlab.com/gitlab-org/gitlab/-/issues/506537#note_2396443367
3. When that setting is enabled, we'll automatically perform a review **IF**
1. The merge request has changes
2. The merge request is **NOT** a draft
1. If a merge request **IS** draft, when that status is removed, we'll automatically perform the review
4. On subsequent pushes to the merge request we would not automatically trigger a review, users would need to explicitly `re-request a review`
### Additional Details
The configuration of this setting should be available in the REST API
issue