Provide new intelligent reviewer suggestions

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

[Part of Intelligent Reviewer Assignment]

We need to provide the new, sorted, algorithm-weighted list of reviewer suggestions to the frontend.

Very high-level, there are two options:

1. Inject the new sorting / algorithm into the existing places reviewers are returned and use a feature flag to control whether it's used.
   • All reviewers eligible for an MR (REST)
   • Reviewers eligible per Approval Rule (GQL)
2. Add a new endpoint specifically for this "grand unified algorithmic reviewer list"

Note: This issue is not for implementing any algorithm or doing any advanced reviewer selection. It's just the "terminus" point for that work: choose / implement how that work would/will get to the front end.