[clang] [CIR] Add NYI cases to builtin switch statement and move existing cases into functions (PR #168699)

[Andy Kaylor via cfe-commits]

andykaylor wrote:

> Could you merge it for me?

No problem merging the PRs, but you've got plenty of merged PRs now. If you want to request commit access, I'd be happy to support the request.

https://github.com/llvm/llvm-project/pull/168699