Utils: Make Layouting a top level namespace

The whole machinery is now almost only layoutbuilder.{h,cpp},
mostly independent of the rest of Utils. Idea is to finish the
separation to make it stand-alone usable also outside creator.

Change-Id: I958aa667d17ae26b21209f22412309c5307a579c
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/python/pythonwizardpage.cpp

@@ -85,7 +85,7 @@ bool PythonWizardPageFactory::validateData(Id typeId, const QVariant &data, QStr
 PythonWizardPage::PythonWizardPage(const QList<QPair<QString, QVariant>> &pySideAndData,
                                    const int defaultPyside)
 {
-    using namespace Utils::Layouting;
+    using namespace Layouting;
     m_interpreter.setSettingsDialogId(Constants::C_PYTHONOPTIONS_PAGE_ID);
     connect(PythonSettings::instance(),
             &PythonSettings::interpretersChanged,