Re-enable benchmarking of symbolic exploration

# Context
We have a small benchmarking framework for the symbolic exploration in the repository (`bench`).
However, it currently gets stuck on the analysis of the `vat` contract.
While the benchmark is currently hardcoded as bytecode, we also have the source code in the repository (`bench/contracts/vat.sol`).
Even though the contract contains `pragma solidity ^0.6.12;`, it can be compiled also with recent `solc` (0.8.27).
The contract itself does not seem that complicated and `hevm` should be able to verify it in a reasonable amount of time.

# Goal

Improve performance of `hevm` on `vat` benchmark and eventually enable benchmarking symbolic exploration again.

This issue will track the progress towards this goal.