update Gnark verifier to reflect all recent changes

[ashpect]

• Transcript and IOPatterns are gone, we need to use narg_string and hints now
• New ZK algorithm implementation
• There is no WhirConfigHidingSpartan anymore
• MerkleTree is no longer in FullPath struct, needs to be consumed by walking over the verifier tree
• SHA256 is the TranscriptHash right now, we should be using Skyscraper2 for recursing

Also closing this #289 issue, since it is a duplicate