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/qmljseditor/qmljscomponentnamedialog.cpp

@@ -34,7 +34,7 @@ ComponentNameDialog::ComponentNameDialog(QWidget *parent) :
     m_checkBox = new QCheckBox(Tr::tr("ui.qml file"));
     m_buttonBox = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel);
 
-    using namespace Utils::Layouting;
+    using namespace Layouting;
     Column {
         Form {
             Tr::tr("Component name:"), m_componentNameEdit, br,

src/plugins/qmljseditor/qmljseditingsettingspage.cpp

@@ -246,7 +246,7 @@ public:
         QObject::connect(useQmlls, &QCheckBox::stateChanged, this, [this](int checked) {
             useLatestQmlls->setEnabled(checked != Qt::Unchecked);
         });
-        using namespace Utils::Layouting;
+        using namespace Layouting;
         // clang-format off
         const auto formattingGroup =
             Group {