refactor: Qt can handle const& in signals and slots

While most Qt types cna use implicit data sharing
pasing our own structs means copies. const& ensure
it's only copied as needed by Qt.

Signed-off-by: Rachel Powers <508861+Ryex@users.noreply.github.com>

launcher/tasks/Task.cpp

@@ -161,7 +161,7 @@ void Task::emitSucceeded()
     emit finished();
 }
 
-void Task::propogateStepProgress(TaskStepProgress task_progress)
+void Task::propogateStepProgress(TaskStepProgress const& task_progress)
 {
     emit stepProgress(task_progress);
 }