Improve exception logging of unobserved exceptions via FireAndForget

Coming from #27076, where the log
output makes finding where the exception arrived for nigh impossible.

osu.Game/Online/Multiplayer/MultiplayerClientExtensions.cs

@@ -23,9 +23,12 @@ public static void FireAndForget(this Task task, Action? onSuccess = null, Actio
 
                     Debug.Assert(exception != null);
 
-                    string message = exception.GetHubExceptionMessage() ?? exception.Message;
+                    if (exception.GetHubExceptionMessage() is string message)
+                        // Hub exceptions generally contain something we can show the user directly.
+                        Logger.Log(message, level: LogLevel.Important);
+                    else
+                        Logger.Error(exception, $"Unobserved exception occurred via {nameof(FireAndForget)} call: {exception.Message}");
 
-                    Logger.Log(message, level: LogLevel.Important);
                     onError?.Invoke(exception);
                 }
                 else