feat: multiple circuits differential fuzzing extension

[Maddiaa0]

Overview

Cleaning

• Flattens the cpp dir so that it is no longer nested

Features

• Adds a templating to the vk and proof generation scripts to support multiple circuits
• Adds a simple Add2 cpp circuit
• Adds a simple Recursive circuit
• Supports multiple circuit selection from the Solidity DifferentialFuzzing library

TODO

• Readme changes

[Maddiaa0]

nice