[llvm] [AsmParser] Don't require value numbers to be consecutive (PR #78171)

[Nicolai Hähnle via llvm-commits]

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

Nice, I've run into this issue in the past and it was always slightly annoying to have to go back and get out the instnamer. LGTM.

Side note: the duplicate argument parsing in `parseArgumentList` is really awkward.

https://github.com/llvm/llvm-project/pull/78171