Multiplayer match screen

[DrabWeb]

Only the basic UI for now, proper functionality to come later.

Partially implements #2723.

[peppy]

Is this one based off a flyte design? If so, best to link the issue or at least a png for comparison.

[DrabWeb]

Probably should've created an issue for this beforehand, sorry. Will remember next time.

[peppy]

I think this is okay to merge now. Would rather avoid PRs of this size in the future; it's very hard to review.

Also with the testing of users and what not, I think we should make central seeders so they aren't being specified all over the test cases. ie. userSeeder.GetUser() would keep returning fresh users with avatars etc. populated, rather than all these inline strings and user blocks in test cases making them long to review and hard to visually parse.