Change OUTPUT_PARTICLE_NAME to be reconstruction-neutral

[mlincett]

Currently config.py specifies:

OUTPUT_PARTICLE_NAME: Final = "MillipedeSeedParticle"

and I believe the key should be made neutral w.r.t. the reconstruction algorithm (i.e. "RecoSeedParticle"), in order to improve readability of the code (although functionally speaking this is irrelevant).

This change would be trivial, if it wasn't for the fact that the key is hardcoded in some test data that would need to be updated, namely pframe pickles at: https://github.com/icecube/skymap_scanner/tree/main/tests/data/reco_pixel_pkls

Note that I would also change OUTPUT_PARTICLE_NAME to something more meaningful such as SEED_PARTICLE_NAME. This is an "output" only from the point of view of the server, but for the client it's an input.

[ric-evans]

@mlincett can this be closed?