Debugger: Integrate setupEngine() into tool start()

... a step towards abandoning the engine-related bits of
the debugger state machinery. The base RunWorker states
meant for that are good enough now.

Change-Id: I3b269bdeb66f14a956b76e6a7e8258f45b3e59e5
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/debuggerruncontrol.h

@@ -126,8 +126,6 @@ signals:
     void aboutToNotifyInferiorSetupOk();
 
 private:
-    void setupEngine();
-
     QPointer<Internal::DebuggerEngine> m_engine; // Master engine
     Internal::DebuggerRunParameters m_runParameters;
     QStringList m_errors;