Improve VisSynchroniser for tomo tiling view.

This PR aims at improving the VisSynchroniser used to sync the 2 tiling views.

It fixes the check of whether the new camera position/scale is close to the previous one or not: It was failing around 0. An absolute tolerance was added to mitigate this.

It prevent calling onFrame (renamed onVisViewpointChanged) in the useFrame when the vis viewpoint didn't changed at all.

This looks to fix the issue of zoom on wheel while under a loop of re-render. There is still some issues with the pan though.