fix: Move BigInt modulus checks to runtime in brillig

[sirasistant]

Description

Problem*

Resolves https://github.com/noir-lang/noir/issues/5373

Summary*

Bigint modulus was checked but never written. Since changing bigint::to_le_bytes to write a modulus ID would require a breaking change, this fixes the modulus issue without changing the opcode spec, by completely offloading modulus checks to the runtime itself.

Additional Context

Documentation*

Check one:

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

PR Checklist*

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