Mithril M3

[vlasin]

Updated Mithril milestones are here (see "New version"):
https://docs.google.com/document/d/1LlolHlHCN8VM9laxrIJa0V7UXP9lJuhWwMxI0r-HouQ/edit?tab=t.0

• Implement a function in Symbolic that checks whether a particular UTxO is in the UTxO set signed by the threshold multisignature (see the existing Mithril.hs module)
• Implement a Plutus script that spends the funds from a UTxO if the ZKP check above succeeds (zkfold-cardano)
• Implement a minimal off-chain code for the script (zkfold-cardano)
• Create a PDF note (no need to include it in the repo) describing the process

NOTE: To make things simpler, the Symbolic function could return a serialized TxOut structure (fixed-size, padded). We then compare it to the output we want to unlock.