Write simple simulations

[clarus]

Context: for now, we focus on the verification of the smart contracts, which are rather complex. We would like to have simpler examples to use as documentation/reference.

Write simulations, with their corresponding proof of equivalence, for a few simple examples that are already there in our Rust test suite. That could be simulations about examples handling the Option type, the Vec type, ...

• write simulations for a few functions found in the translated Rust examples
• show that these simulations are equal
• add links to these examples in our Mardown documentation or even the README of the project