Previously `plonk::verify_proof` took an `MSM` as an argument, to enable
batch verification. However, this also required that it take a source of
randomness in order to enforce separation of proofs within a batch. This
made single-proof verification unnecessarily non-deterministic.
We now have a `VerificationStrategy` trait encapsulating the necessary
details, and separate `SingleVerifier` and `BatchVerifier` structs for
the specific variants. Proof verifiers no longer need to create and
manage the `MSM` themselves, and single-proof verifiers no longer need
to supply a source of randomness.
Co-authored-by: Sean Bowe <sean@electriccoin.co>
Jack Grigg