[Feature] Load groth16 proofs from disk

[capossele]

From @mothran feedback: "I would also love an example of having a unit test with the proof is baked on disk + script to regenerate all the proof test data. Because generally I don't need to rerun the proof for each forge test through bonsai/locally, if we had a cheat code to get the data like seal + journal + post_state from a .json on disk that would be awesome"