feat(acir)!: Add Keccak256 Opcode

[kevaundray]

Related issue(s)

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Resolves #90

Description

Keccak256 looks exactly the same as Blake256 and Sha256 from an opcode perspective, so it was mostly just giving it an opcode number and copying the function definition from sha256

Summary of changes

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Dependency additions / changes

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Test additions / changes

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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.

Additional context

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