feat: add nargo preprocess command

[TomAFrench]

Related issue(s)

Extends work done on #873 to cover nargo compile.

Description

Summary of changes

This PR adds the nargo preprocess command which accepts an ACIR file and generates proving and verification keys from it.

The motivation behind this is to decouple compilation and preprocessing, e.g. after compiling a noir program to a CompiledProgram we can initially generate a set of keys to prove against barretenberg however we may want to start generating proofs against gnark in future. Using nargo preprocess you could prove against the exact same CompiledProgram as you were before.

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

[jfecher]

LGTM

[kevaundray]

PR looks good -- going to remove this from the queue and release 0.3