Replace proof of fairness with a PDL with Slack proof from GG18/20

[elichai]

This utilizes the PDL With Slack ZK proof from GG18/20 (https://github.com/ZenGo-X/multi-party-ecdsa/tree/master/src/utilities/zk_pdl_with_slack) and uses range-proofs from https://github.com/ZenGo-X/multi-party-ecdsa/pull/145 to validate it. Also added a check for the moduli size to make sure it's ~2048 bits.

I still need to update the Readme to remove any mention of the fairness proof