Utils: Make the second parameter to LayoutBuilder::attach() an enum

More explicit and more potential options (e.g. "treat grid as form")
than a bool.

Change-Id: I89413efe30410160c38b0e524ba64288dde2332e
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/python/pythonsettings.cpp

@@ -114,7 +114,7 @@ public:
         Form {
             Tr::tr("Name:"), m_name, br,
             Tr::tr("Executable"), m_executable
-        }.attachTo(this, false);
+        }.attachTo(this, WithoutMargins);
     }
 
     void updateInterpreter(const Interpreter &interpreter)