Utils: Flatten LayoutBuilder related hierarchies

Originally the idea was to only expose LayoutBuilder, but we
are getting more and more related items. Be consequent now,
and have everything in Utils::Layouting, but not in nested classes.

Change-Id: Ic0f98595882e5c60a25c30ec52df4a0ea79bc0ca
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/cmakeprojectmanager/cmakekitinformation.cpp

@@ -50,6 +50,7 @@
 
 using namespace ProjectExplorer;
 using namespace Utils;
+using namespace Utils::Layouting;
 
 namespace CMakeProjectManager {