When creating and MR rule, improve searching for MR reviewers

Problem to solve

When I want to create an approval rule, usually I want to set the approvers from my organization. However, when I search in the search field, unrelated groups from other organizations show up first.

Current Behavior

Today, the default is set to search in all groups across GitLab.com. It appears that we do some filtering so the first time the user clicks into the field there are mostly relevant suggestions, but once I start typing those are lost and I'm getting results for all of GitLab.com.

Searching for groups today

Desired Behavior

The preferred behavior is for the search to be scoped to the user's available groups.

Proposal

1. Change the "search in all groups" options to say "search all of GitLab.com" or similar nomenclature that makes it clear you're searching across public GitLab.
2. Change the default search to search only groups the user has access to (probably would require a naming update?)
3. Improve the ranking of results when users search for groups, so that they are more likely to see relevant groups.