Better model and deserialize the Solidity compiler output used to decode stack traces

[Xanewok]

In #545 we migrated 1:1 the logic from Hardhat (TypeScript) to deserialize the Solidity compiler standard JSON input/output and convert this into a "build model" that's used to decode the stack traces.

The original code was translated quite literally, so there's a lot of serde_json::Value usage and manipulation. We should model the deserialization for the input/output more declaratively rather than accepting a JSON blob and doing the conversion ourselves.