Code dedup for utils function shared between tests and bench across crates

[alxiong]

Currently, there are some util functions that we only want conditionally compile for tests and benches across different crates. (specifically gen_srs_for_testing here)

We currently directly copy the code from jf-primitives inside our snark.rs::universal_setup_for_testing(), which is not ideal. We should try to de-duplicate this later.

initially proposed: https://github.com/EspressoSystems/jellyfish/pull/231#discussion_r1175419699