[llvm] [NFC][AsmWriter] Add emitMDNodeAnnot (PR #198317)

[Harald van Dijk via llvm-commits]

hvdijk wrote:

> I'm not sure what standard you mean, but this is adding new functionality that will later be used.

I mean when only this PR on its own is merged, no behaviour of any command-line utility changes, and that's why there is no test in this PR. That's the rationale for why many prior commits have been labelled as NFC, which subsequently ended up breaking downstream code because they by design changed the public API of libLLVM and should, in my opinion, absolutely not have been labelled NFC.

> IMO we should just drop the convention of using NFC. It's misused most of the time

That sounds fine to me, I'll remove [NFC] from the title.

I see CI is failing after the merge of `main`, it was a merge of a point where `main` was broken, merging again to confirm that CI will pass after that.

https://github.com/llvm/llvm-project/pull/198317