Deduplicate shortest path code

[visr]

The code was identical except for comments and print statements. So now we move it all into a single function that is part of the package, so the individual scripts are just a few lines.

Only AGV was an outlier since it had a lot of code after the shared code. Perhaps @rbruijnshkv can comment on if that is needed or not. Another difference I noticed is this, AGV has this set to 5:

        distance_interval = 50  # The distance interval you want to segment the lines at

This only deduplicates, I didn't want to start modifying the code at the same time. So I cannot run it since it relies on local paths that I don't have.

[rbruijnshkv]

Went through it quickly, it seems okay! Changes in this part of the code are by the way not expected to break the code later on, but at most the visualization (which is not necessarily inferior).