Move some work out of zkVM

[mohamedalichelbi]

To improve proof generation times, it could be helpful to do some things outside of the zkVM without compromising any security properties. An example would be to compile scripts outside of zkVM, and only send serialized AST as input to the zkVM. After that, verifiers can compile scripts on their side as well, make sure they obtained the same AST as the one exposed by the ZK-Proof, and hence be sure that the provided script is exactly the one used by the holder