Gui: Use getObject<T>() helpers in classes

This commit is generated using regex based find and replace:

```
s/[\w:]+_cast\s*<([^>]+)\*>\s*\(\s*getObject\(\s*\)\)/getObject<$1>/
s/[\w:]+_cast\s*<([^>]+)\*>\s*\(\s*([^)]*)\s*->\s*getObject\(\s*\)\)/$2->getObject<$1>()/
```

To regenerate if needed.

src/Mod/Fem/Gui/ViewProviderSetElementNodes.cpp

@@ -37,7 +37,7 @@ PROPERTY_SOURCE(FemGui::ViewProviderSetElementNodes, Gui::ViewProviderGeometryOb
 bool ViewProviderSetElementNodes::doubleClicked()
 {
     Gui::TaskView::TaskDialog* dlg =
-        new TaskDlgCreateElementSet(static_cast<Fem::FemSetElementNodesObject*>(getObject()));
+        new TaskDlgCreateElementSet(getObject<Fem::FemSetElementNodesObject>());
     Gui::Control().showDialog(dlg);
     return true;
 }