Core/Utils: Migrate further to Utils::Id

The coreplugin/id.h header is kept for downstream for now.

Change-Id: I8c44590f7b988b3770ecdc177c40783e12353e66
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/scxmleditor/scxmleditordata.cpp

@@ -51,6 +51,7 @@
 
 using namespace ScxmlEditor::Common;
 using namespace ScxmlEditor::PluginInterface;
+using namespace Utils;
 
 namespace ScxmlEditor {