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/vcsbase/wizard/vcsconfigurationpage.cpp

@@ -66,6 +66,7 @@
 
 using namespace Core;
 using namespace ProjectExplorer;
+using namespace Utils;
 
 namespace VcsBase {
 namespace Internal {