Issue with 3D GPU regularisers in v. 24.0.0

[dkazanc]

Thanks a lot for refactoring guys! While I was fiddling with the toolkit to make it work for ToMoBAR, I noticed that the output volumes in demo_gpu_regularisers3D.py are not good (see the image below). That is also consistent across all regularisers.

I've tested 2D regularisers and they seem to be OK, so it is only 3D by the look of it. I know that input parameters have been slightly reshuffled for modules, so I checked that they in accordance to low-level functions. Doesn't seem to be the issue. In addition, the CuPy methods do produce correct results, so it must be something else. See that to reproduce the image below I've changed parameters slightly. We need to add 3D tests :)