Core/Utils: Migrate further to Utils::Id

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

Change-Id: I8c44590f7b988b3770ecdc177c40783e12353e66
(cherry picked from commit 430a33dcd9)
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/projectexplorer/sessionmodel.cpp

@@ -29,7 +29,6 @@
 #include "sessiondialog.h"
 
 #include <coreplugin/actionmanager/actionmanager.h>
-#include <coreplugin/id.h>
 
 #include <utils/algorithm.h>
 #include <utils/fileutils.h>
@@ -39,6 +38,7 @@
 #include <QDir>
 
 using namespace Core;
+using namespace Utils;
 
 namespace ProjectExplorer {
 namespace Internal {