Update function in XRManager.cs only needs to be run once per scene change.

[JacobChrist]

Update function in XRManager.cs only needs to be run once per scene change. Probably tap off the network scene change event.

Currently this is running in Update(), doesn't seem to be bogging down the game but my computer is smoking fast compared to a Quest.

    private void Update()
    {
        // todo: 3 We should only need to do this once when we changes scenes.
        if (sceneCamera == null) sceneCamera = GameObject.Find(sceneCameraName);
        if (xrOrigin == null) xrOrigin = GameObject.Find(xrOriginName);

        switch (controlMode)
        {
            case ControlMode.MouseKeyboard:
                if (findCameras())
                {
                    sceneCamera?.SetActive(true);
                    xrOrigin?.SetActive(false);
                }
                break;
            case ControlMode.XReality:
                if (findCameras())
                {
                    sceneCamera?.SetActive(false);
                    xrOrigin?.SetActive(true);
                }
                break;
        }
    }