chore(nargo): report bubbled up errors using eyre

[TomAFrench]

Related issue(s)

Resolves #819
Resolves #686

Description

Summary of changes

Rather than explicitly writing errors to the console and then calling std::process::exit(1) we now wrap the bubbled up error in an anyhow::Result and just return it from main.

Dependency additions / changes

Added anyhow as dep of nargo.

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

[Ethan-000]

I think this also resolves #686

[TomAFrench]

Ah, thanks yes it does (as we no longer colour the terminal on errors)

[jfecher]

I'm not sure if it's worth it to add a new dependency just to avoid writing:

if let Err(err) = result {
    err.write()
}

[phated]

I usually agree with @jfecher about adding dependencies but I think getting anyhow into the project would be helpful for the future. It's one of the (surprisingly) few crates that I've seen recommended by everyone (probably just thiserror and anyhow!)

[TomAFrench]

Actually, it looks like our existing dependency of color_eyre can perform much the same role as anyhow would here.