chore(nargo)!: rename contract command to codegen-verifier

[TomAFrench]

Related issue(s)

Resolves #945

Description

Summary of changes

I've renamed the nargo contract command to nargo codegen-verifier. codegen is shorter than generate and is more descriptive so I opted for this name instead of what's discussed in #945 (happy to switch if there's strong feelings about this).

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

[kevaundray]

Did you consider 'gen-verifier' ?

[TomAFrench]

Yeah, I did. It felt a little too abbreviated in my mind. "codegen" is a well-known term but "gen" has no meaning until the user makes the leap to "generate"

[kevaundray]

Fair, I have no strong opinion re this. Quick ping to @noir-lang/tooling

[kevaundray]

I pinged @joss-aztec since he replied to the original issue and he says your new suggestion is even better