improve roi.register_very_offset_images

as of a958df05, roi.register_very_offset_images is working but is taking twice as long as it would need to.

this is because register_very_offset_images internally loops over the data twice (once with a data transformation and once without) and repeats all operations. This has historical reasons.

Now, this is not necessary anymore.

To fix this, simply revert cd5c1f5d

I kept this like this to have E2E tests succeed but it should be noted that this could be fixed with next image building