Migrate PyJet dependency to FastJet

[jacanchaplais]

I noticed an ImportError when trying to import graphicle, due to a missing symbol from a C library. I am unsure whether this is to do with an instability in the latest release of the C libraries, or due to PyJet's dependencies no longer keeping up to date, but it seems now is a good time to migrate to FastJet. This will add dependencies of awkward under the hood, but the same functionality can be achieved.

Specifically, using the fastjet.ClusterSequence constructor, and calling the .constituent_index() method achieves the same thing as the structured array approach, with the index inserted in as a field before clustering. The only difference appears to be that these clusters are not sorted by $p_T$, so make sure to do this before yielding the results out.