[Feature] Support deployment `config.toml` files with our own library

[nategraf]

We currently some code sitting in the Foundry template for handling deployment configs. In particular, it helps the user specify which verifier they want to use on the chain they are deploying to. It is also generally useful for many smart contract deployment scenarios.

https://github.com/risc0/risc0-foundry-template/blob/main/script/Deploy.s.sol#L49-L70

This code should live in and be maintained in this repo, instead of simply existing in the template.