[llvm] [GlobalISel][TableGen] Take first result for multi-output instructions (PR #81130)

[Pierre van Houtryve via llvm-commits]

https://github.com/Pierre-vh approved this pull request.

LGTM but wait for @arsenm to comment, I'm really wondering about those instselect test changes

https://github.com/llvm/llvm-project/pull/81130