Suggest approvers in merge request - UX improvements

Resources

PM @victorwu | FE @lbennett

Problem

• In the existing implementation, the suggested approvers is below the entire section. It is not that helpful when you are actually choosing approvers.

* The new design of approvers selection (per project, and per merge request), is here: https://gitlab.com/gitlab-org/gitlab-ee/issues/1738 * This issue will also help with the selection of approvers themselves: https://gitlab.com/gitlab-org/gitlab-ee/issues/1593.

Scope

• Re-design the UX of the suggested approvers to be inline with the above new design.
• The suggestion BE algorithm itself does not change. The scope of this issue is just integrating that suggestion on the FE in a coherent manner.
• The BE algorithm to change suggestions will be worked on in separate issues.

• This applies to the project settings area. The same area in the merge request web form should also be updated, but is a stretch goal for this issue. (I.e. if it's minor extra effort and can be done together easily without delay, let's include it as well.)

Design

Add an approver / a group as an approver suggestion for each merge request was replaced by Suggested approvers: Username.