[llvm] CodeGen: Suppress per-invoke EH labels via an MCAsmInfo object predicate (PR #225903)

[Reid Kleckner via llvm-commits]

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

This caused me to read the LangRef docs for exception-handling flags, and I noticed a bug, and fixed it unilaterally: #226025

Anyway, yes, not emitting labels up front seems better.

I decided not to pick nits over "per-invoke" EH labels. To my recollection, all label-based EH schemes put labels around individual invokes, so it's really a "use labels" flag, but that's not very important, and I'm not 100% confident in those beliefs.

https://github.com/llvm/llvm-project/pull/225903