Use unique name with timestamp instead of subdirectory for legacy upload

This prevents issues with Arma 3 not being able to load scenarios.

Command/Upload/UploadCommand.cs

@@ -101,7 +101,8 @@ protected async Task SteamRemoteStorageUpload()
             }
 
             var fileName = (new FileInfo(Path)).Name;
-            var tempPath = NormalizePath($"kp-steam-tmp/{fileName}");
+            var timestamp = DateTime.Now.ToString("yyyyMMddHHmmssffff");
+            var tempPath = NormalizePath($"kp_steam_cli_{timestamp}_{fileName}");
             var fileContent = File.ReadAllBytes(Path);
 
             Logger.LogDebug($"Copying file to temp path \"{tempPath}\"");