Converting methods inside NSW clustering to const and introducing a property for the allowed hole size in the sTGCs

This MR turns the methods of the NSW cluster builder tools into const. For the MM this was already the case but the const keyword was missing. For the sTGC the member variables m_clustersStripNum and m_clusters were replaced by variables inside the function call. Also the counting mismatch between multilayer, gas gaps and vector indices was solved by subtracting minus one from the multilayer and gas gaps, reducing the array dimensions by one. Furthermore, the hard coded hole size inside the sTGC clustering becomes a property replacing the property allowHoles

This MR needs to stay WIP until !30473 (merged) is merged

Adding @rosati, @nkoehler