After switching `UserLookupCache` to `GET /users/lookup` from `GET
/users`, multiplayer sort of breaks, since the former endpoint does not
return `ruleset_statistics`, which are used in multiplayer to show
users' ranks. Therefore, switch multiplayer to use the appropriate
request type directly.
These can be tested by adding a `Task.Delay(3000);` at the end of the
`MultiplayerClient.JoinRoom` task. The reason is typically that
`Client.Room` becomes not-null but the join task still hasn't completed
yet, so e.g. the ready button is still disabled.