Production-candidate STM library for IVC SNARK #3377

Why

The MVP of the recursive SNARK proofs (#2529) delivered a working IVC implementation in the mithril-stm library, but it is not production ready: the circuits are still partly coupled to the underlying proving library, some off-circuit checks are missing, the recursive and non-recursive implementations have diverged, the testing strategy is slow and incomplete, and the documentation does not cover the recursive scheme.

What

Bring the IVC SNARK implementation of the mithril-stm library to a production-candidate state: harden and optimize the circuits and the proving pipeline, complete the missing verification checks, harmonize the recursive and non-recursive implementations, make the library usable by default, and deliver the testing strategy and the documentation which back it.