[PTRun] Implement thread-safety in query results task with lock (#34009)

* [PTRun] Implement thread-safety in query results task with lock

* [PTRun] Lock is moved to Unit Converter Query function.

* [PTRun]  _updateSource.Token is used instead of local currentCancellationToken to avoid dangling reference.

src/modules/launcher/Plugins/Community.PowerToys.Run.Plugin.UnitConverter/Main.cs

@@ -50,7 +50,6 @@ namespace Community.PowerToys.Run.Plugin.UnitConverter
                 return new List<Result>();
             }
 
-            // Convert
             return UnitHandler.Convert(convertModel)
                 .Select(x => GetResult(x))
                 .ToList();