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/mesonprojectmanager/settings.cpp

@@ -45,7 +45,7 @@ GeneralSettingsPage::GeneralSettingsPage()
 
     setLayouter([](QWidget *widget) {
         Settings &s = *Settings::instance();
-        using namespace Utils::Layouting;
+        using namespace Layouting;
 
         Column {
             s.autorunMeson,

src/plugins/mesonprojectmanager/toolkitaspectwidget.h

@@ -36,7 +36,7 @@ private:
 
     void makeReadOnly() override { m_toolsComboBox->setEnabled(false); }
 
-    void addToLayout(Utils::Layouting::LayoutBuilder &builder) override
+    void addToLayout(Layouting::LayoutBuilder &builder) override
     {
         addMutableAction(m_toolsComboBox);
         builder.addItem(m_toolsComboBox);