Debugger: Replace the QVariant callback cookies by direct parameters

Lambda makes it possible.

Change-Id: I26a4df71dcd24b76a4f0d6d67545b2e1c6ba2412
Reviewed-by: hjk <hjk@theqtcompany.com>

src/plugins/debugger/debuggerprotocol.h

@@ -191,7 +191,6 @@ public:
     int            token;
     ResultClass    resultClass;
     GdbMi          data;
-    QVariant       cookie;
     QByteArray     logStreamOutput;
     QByteArray     consoleStreamOutput;
 };