fix: correct type checking to handle false bools

[TomAFrench]

Related issue(s)

Resolves #889

Description

Summary of changes

FieldElement.num_bits() returns 0 for `FieldElement::zero() so the current check for satisfying the AbiType fails. I've relaxed the check to accept 0 or 1 bits to address 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.
• This PR requires documentation updates when merged.

Additional context

[jfecher]

I think we should change num_bits itself to return 1 bit for the value 0 since we still need to store it somewhere. Would require some testing though.

[TomAFrench]

Yes, that's true. As that requires us to bubble up changes to ACIR, let's just switch this to an explicit 0 or 1 check (field value, not num bits) for the time being.