Representation of a processed STV.
(processed-stv-p x) is a std::defaggregate of the following fields.
You should probably read stv-implementation-details to understand these fields.
Historically we had another field that could also optionally store pre-computed snapshots for debugging. We took this out because it could make stv-run a lot slower during GL proofs. The snapshots were huge, and this really slowed down GL's gl-concrete-lite check.