Participant routing feature: needed improvements

[Didayolo]

The group feature got merged:

• Feature group routing for submissions #2393

Remaining TODO:

• The leaderboard should NOT show the group column when no groups have been set
• Add documentation
• Add tests
• Rename button "Edit" to "Save"
• Rename the feature ("participant routing", "add participant routing group")
• Add a question mark with expanation in the editor
• The queue search is not convenient (Autocomplete for queue selection #2430):

[acletournel]

Other naming suggestions from Sylvain: "Compute Profiles", "Evaluation backends" or "Runtime queues". I vote for "compute profiles". "Evaluation backends" is confusing as well as the word "queue" in "runtime queues"