[Proposal] Infrastructure for various-scale universal parameters

[weikengchen]

💥 Proposal

In a setup phase, we may set up for large parameters such as for 2^28. This is essentially a committer key for the polynomial commitment.

However, most statements are small, we want to enable a user to download only a subset of the committer key, which is technically doable, and we just need an infrastructure to do so.

• a function that trims the KZG parameters down to different sizes
• ability for snarkvm-parameters to retrieve URS of different sizes

[weikengchen]

An enhancement of the SNARK trait is also proposed:

SNARK trait could be updated to have universal_setup() and circuit_setup() whereby Groth16 would have unimplemented!() in universal_setup()` and Marlin’s circuit_setup() would only use a trimmed SRS to index.

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This will allow us to use the Marlin's specific interface as well as keep the old interface for Groth16.