Pairwise telescope positions

The application of the cross-calibration algorithm requires as input the pairwise distances of the telescopes of the array. Once the array is constructed, that will probably be a stable text file. However since we are currently in the design phase of the array (but also have in mind the application of the calibration algorithm to other arrays) we probably need a dynamic way to produce the telescope distances, in the x-y plane (TBD: do we need to account for the differences in telescope altitudes?)

A way to go would be to implement a function here: https://ctapipe.readthedocs.io/en/latest/api/ctapipe.instrument.SubarrayDescription.html

Alternatively, one could produce it via the Corsika config file or via sim_telarray files.