fix: add more readable error for missing argument in toml

[TomAFrench]

Related issue(s)

Resolves the second part of #969

Description

Summary of changes

Previously we'd iterate over the fields in Prover.toml, assume there's a matching entry in the ABI and then decode the data. This throws an unhelpful panic if Prover.toml contains an entry which doesn't exist in the ABI when looking up its type.

I've updated this loop to instead work over the expected ABI fields, check if an entry exists in Prover.toml and if not we raise an error saying that the argument with a certain name hasn't been found. As part of this we now pass the argument name into try_from_toml so that we can throw a meaningful error for struct fields.

Dependency additions / changes

Test additions / changes

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.

Documentation needs

• This PR requires documentation updates when merged.

Additional context

[jfecher]

👍