Add skeleton for porting Nova verification

[storojs72]

This solid PR contains a bunch of contracts that allow starting the porting process of Nova's CompressedSnark verification from Rust to Solidity.

The list of contribution is following:

• Poseidon contracts (for both Pallas and Vesta curves) which produce compatible hashes with Neptune. Contracts implement Poseidon using parameters (constants, modes, state size) similar to Nova;
• SAFE API contracts, also compatible to Neptune (it is important to have them, since verifier uses Poseidon via this API);
• Step 1 of CompressedSnark verification - which is essentially a bunch of trivial checks of input data lengths;
• Step 2 of CompressedSnark verification - this is a part of verification where Poseidon is used (checking if the output primary hash in R1CS instances point to the right running instance);
• Python utility scripts that allows generating contracts-helpers for loading relevant information (CompressedSnark and VerifierKey hardcoded instances) into EVM memory - necessary for debugging.

Currently (for simplicity) we fix actual proof and key for its successful verification (we use this example from Nova) in order to have some stable data source. That is why appropriate JSONs are also committed.

[mpenciak]

I think this looks good, it has a few TODOs that may be worth tackling before merging though?

[mpenciak]

It may be worth adding a comment on these generated .sol files pointing to the python script that generates them.

[storojs72]

It makes sense

[mpenciak]

Same here

[storojs72]

it has a few TODOs that may be worth tackling before merging though

Do you have something in particular? I added #5 and #6 issues which seems to be a good tasks for newcomers, rest TODOs - comments in code - seem to me an important things but do not worth the time at the moment