Improve Test Config Ergonomics

[ControlCplusControlV]

          We don't need to do this in this PR, but start thinking about how we could make the config flow nicer. This code makes me think that we should have a variant of `testConfig` that accepts a ERC4626 token and derives the base token and the initial share price from the vault.

Originally posted by @jalextowle in #454 (comment)

[jalextowle]

We've added a testConfig() function and use it in many places.