Suggest / default assignee for merge request

• Often when you create a merge request to get code into a repo, you don't know who the maintainer is. You don't know who to grab attention. Maybe it's an open source project. Maybe you are in a large internal organization (inner sourcing). And you want to contribute, but you don't have all the context.
• You can read the README.md and other docs. But the tool should be smart in giving you an assignee.
• When creating a merge request, have a default assignee or at least suggest one.
• Based on some logic on the repository itself. For example, it could be based on whose made the most commits/changes to the repo in the recent past. More complicated logic possible. But that could be a good start.
• This is similar to default / suggesting approvers.

changed milestone to %Next 3-6 months

added Discussion label

As suggested by @JobV

Thanks for the inspiration @jramsay

marked this issue as related to #19570 (moved)

marked this issue as related to #3126 (moved)

added feature proposal label