fix(abi): ensure that return value is loaded from toml

[TomAFrench]

Related issue(s)

Resolves #860 (review)

Description

Summary of changes

When loading inputs from toml we need their AbiType to be included in the map abi_map. Due to #865, this doesn't get inserted automatically so we panic when loading return values.

We now insert the return type into the map so we can load toml files correctly again.

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.
• This PR requires documentation updates when merged.

Additional context

[vezenovm]

Fix looks good to me. I just ran into it when trying to run nargo prove and nargo verify separately rather than nargo prove --verify. The separate prove and verify commands are now working for me

[TomAFrench]

Yeah, I tend to use nargo prove --verify quite a bit so this slipped through when testing locally. We should potentially re-add some integration tests which write to file as we used to in order to catch stuff like this.