Fix broken tip displacement calculation

[mondracek]

Fixes #387.

• The crucial line to be fixed was in ppafm.HighLevel.perform_relaxation().
• I have added the --dist option to examples/FFPB_KPFM/run.sh so that we have some example that checks the --dist functionality in the future.
• The change I have made in the relaxTipStrokes_omp function in ppafm/cpp/ProbeParticle.cpp is optional. The old definition of ioff values combined with the new definition of index order resulted in an erratic scanning of tip position in the x,y directions. The code still worked because all points would be eventually visited, although in a nonsensical order, but I thought it would still be better to make it consistent with the new index order.
• Finally, I have removed the meshgrid3d function from ppafm/HighLevel.py. It did nothing and could not do anything as it lacked any command for output: neither it had a return command nor did it any argument reassignment. It caught my attention when I was checking how the np.meshgrid function works in the line I had to fix.

[mondracek]

By the way, I had to commit this with git commit --no-verify, otherwise, I was getting
ERROR: Package 'isort' requires a different Python: 3.9.12 not in '>=3.10.0'.
As I understand it, it is because my git commit calls an old version of Python for the pre-commit checks. Sorry for that, I do not have a full control over the software versions used on our computer grid. I suppose I could move my ppafm installation to some virtual environment where I would install my own pip and git, but it seemed to be too much hassle to do it at this moment (especially as I am not completely sure whether it would helped or not).

[NikoOinonen]

I see ioff was in the wrong order. I don't understand transpose order in the meshgrid, but I trust you tested that it works.