Utils: Move C++ language details from ProjectExplorer to Utils

We want to use them in the backend processes too so it's nice to share them
in Utils. A concrete size was added too because they should be serialized.

Change-Id: Id5eb8f46643d5159f034fc9559f68a08d7e5847a
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cpptools/cppprojectinfogenerator.h

@@ -48,7 +48,7 @@ private:
                                        const ProjectFiles &projectFiles,
                                        const QString &partName,
                                        Language language,
-                                       ProjectExplorer::LanguageExtensions languageExtensions);
+                                       Utils::LanguageExtensions languageExtensions);
 
 private:
     const QFutureInterface<void> m_futureInterface;