Refactored ACET's "Yes(C)" definition for simplicity

[randywoods]

Got rid of answerButtonDefs - it wasn't being used

🗣 Description

ACET's "Yes(C)" should only be applied in the ACET skin. The answer definition was refactored into the main structure with a skin property to simplify this and keep the answer definition where you expect it to be.
The old answerDefs collection has been removed -- it hasn't been used for awhile and should be removed.
The answer lookup was tweaked a bit to account for any "skinned" answer options (ACET's Yes(C) being the only one currently).

💭 Motivation and context

🧪 Testing

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.