feat(cli)!: Add --unstable-features to gate unstable features

[jfecher]

Description

Problem*

Resolves #7423

Summary*

Adds the CLI flag --unstable-features (or -Z) to nargo for all compile sub-commands which accepts a list of unstable features to enable. Without this, usage of these features is now a hard error (previously a warning), making this a breaking change. The list of features to accept can be separated by commas: -Zenums,array-ownership or by specifying the same flag multiple times: -Zenums -Zarray-ownership.

Currently the only unstable features are:

• Enums
• Array ownership (reserved for future experimentation with & and move semantics for arrays)

Additional Context

I'm using the name "unstable features" to match rust a bit more closely although previously we used "experimental features." I'm open to naming debates since this is a public facing flag we shouldn't change once it is stabilized.

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jfecher]

Hmm looks like CI is broken for some reason because I added a new workspace package. I'll resolve it after lunch but the PR should still be ready for review.

Edit: Completely missed the new crate in git since it was in utils instead of compiler 🤦‍♂️.

[michaeljklein]

LGTM