Outer Recursion Circuit: halo2 custom gate for poseidon2 #1134
Description
Currently the static STARK-to-SNARK verifier circuit is compiled entirely to halo2-base. In particular the poseidon2 implementation is entirely in halo2-base. It is expected to be much more optimal to use a custom halo2 gate for Poseidon2.
This will need to use a decorator pattern to have a vanilla halo2 circuit alongside halo2-base circuit. This has been done before for keccak here.
Blocked by #1135