CppTools: Move CppHoverHandler to CppTools

This is in preparation for clang code model to provide its own hover
handler.

Change-Id: Ifbdd96f427989bd5d1fbc4badb9c38108485c2f2
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/plugins/cpptools/cppmodelmanagersupportinternal.h

@@ -41,6 +41,7 @@ public:
     virtual ~ModelManagerSupportInternal();
 
     CppCompletionAssistProvider *completionAssistProvider() final;
+    TextEditor::BaseHoverHandler *createHoverHandler() final;
     BaseEditorDocumentProcessor *createEditorDocumentProcessor(
             TextEditor::TextDocument *baseTextDocument) final;
     FollowSymbolInterface &followSymbolInterface() final;