Implement SNARK-friendly changes in STM library #2795
Description
Why
We need to refactor the STM library in order to make it SNARK-friendly. Following the definition of the architecture in #2763, we have defined an implementation plan and we want to address the refactoring part of the plan as a first step.
What
Implement SNARK-friendly changes in the STM library.
How
- Update the Merkle tree to support multiple leaves (for concatenation and following proof systems)
- Update the key registration to support the new Merkle tree structure
- Move responsibility of creating single signature artifacts to the concatenation proof system (in the
proof_systemmodule)