RASCIL simulation leads to black dirty images

[mpluess]

Tested with karabo.simulation.sample_simulation.run_sample_simulation as well as karabo.test.test_simulation.test_backend_simulations. On the example of test_backend_simulations, I verified that the problem is not the recently introduced export_visibility_to_ms call for the output. It's the same if one uses the generated visibilities before writing them to disk. I also verified that us not having the RASCIL data dir (see https://developer.skao.int/projects/rascil/en/latest/RASCIL_install.html#installation-via-pip) is not the problem.

• [ ] Lukas mentioned there might be a different RASCIL data dir, apart from the one mentioned @ https://developer.skao.int/projects/rascil/en/latest/RASCIL_install.html#installation-via-pip, which we might be missing, which in turn might lead to simulations not working. Probably a direction that should be investigated.
• [ ] Check if the RASCIL output in karabo.simulation.line_emission.py is still okay (Luis investigated differences between OSKAR and RASCIL on this example, so RASCIL should've been running fine when he merged this, at least on his machine)
• [ ] Investigate and fix
• [ ] Verify dirty image turns out the same, regardless of using generated visibilities before writing them to disk or using the disk export after export_visibility_to_ms
• [ ] Remove NotImplementedError for RASCIL backend @ karabo.simulation.sample_simulation.run_sample_simulation
• [ ] Include RASCIL simulations again @ karabo.test.test_sim_format_imager_combos

[sfiruch]

We should check if "Re" and "Im" parts of visibilities are zeros.