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

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > I wouldn't call this NFC
> 
> It's not NFC for LLVM-as-a-library but it's NFC for all of the LLVM command-line utilities. It's annoyed me for years that's been the standard by which we judge what is and isn't NFC, 

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

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

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