[clang] [CIR] Upstream support for emitting ignored statements (PR #130869)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

Would be neat if the IR test was:
->CIR
->CIR->LLVM
AND
->LLVM

it sets the precedent for our 'future' and makes it easier to have a test form of the "converted" tests later, and makes it easier to review for correctness, but I'm willing ot let the group discuss it.

Else, I'm good with this.

https://github.com/llvm/llvm-project/pull/130869