Plotting `CartesianPoints` does not seem to be correct

[fhagemann]

After having merged #489, the plotting of CartesianPoints seems to be wrong.
Look at this plot in the documentation:
https://juliaphysics.github.io/SolidStateDetectors.jl/main/tutorials/complete_simulation_chain_IVC/#Simulation-of-charge-drifts

[fhagemann]

I assume that the points/units are not properly converted, so they are actually plotted in units of mm, rather than m.

[fhagemann]

This seems to be the commit that broke it: 71f1435