Do not store pause state in ControlToolBar...

... Move that into ProjectAudioManager instead, and update the button, only to
reflect it, in idle time.

However, AudioIO also has its mPaused member variable, and it is not obvious
that it was always kept the same as the button state.  No attempt was made
here to identify and fix any bugs, but only to preserve behavior.

src/ProjectAudioManager.h

@@ -35,6 +35,10 @@ public:
    void SetTimerRecordCancelled() { mTimerRecordCanceled = true; }
    void ResetTimerRecordCancelled() { mTimerRecordCanceled = false; }
 
+   bool Paused() const { return mPaused; }
+
+   void SetPaused( bool value ) { mPaused = value; }
+
 private:
    // Audio IO callback methods
    void OnAudioIORate(int rate) override;
@@ -48,6 +52,8 @@ private:
 
    //flag for cancellation of timer record.
    bool mTimerRecordCanceled{ false };
+
+   bool mPaused{ false };
 };
 
 AudioIOStartStreamOptions DefaultPlayOptions( AudacityProject &project );