Support additional proof systems

[oskarth]

This issue is a stub and will be filled in with more detail.

We want to support additional proof systems outside of just Circom/Groth16. This can easily be added to mopro-core: https://github.com/oskarth/mopro/tree/main/mopro-core/src/middleware

Interesting candidates:

1. Halo2 (existing developers, Rust lib easy to integrate)
2. Spartan (modern, good for mobile memory/GPU)
3. Nova/Folding schemes (modern, good for mobile memory/GPU)

Notes:

• For Nova/Folding Nova Scotia requires upstream work to get rid of binary shell out (not allowed on e.g. iOS)
• Once github.com/privacy-scaling-explorations/folding-schemes/ is more mature makes sense to integrate this

[oskarth]

Experimental Kimchi (used in Mina blockchain, backend for o1js) support here #34

[oskarth]

Noir is also relevant

[oskarth]

Holonym VOLE prover for very fast alt proof system that trades off succinctness (good for non-blockchain use cases), used in some ZK Identity solutions: https://github.com/holonym-foundation/vole-zk-prover