Test for Groth16 verifier with no public inputs

[jonas-lj]

          Approving, but we need to follow with upcoming PRs:

a) test against NO public inputs (empty), @benr-ml wdyt? b) @benr-ml what about the reported memory leak from auditor?

Originally posted by @kchalkias in https://github.com/MystenLabs/fastcrypto/pull/469#pullrequestreview-1324858566