[llvm] [DXIL] Model DXIL Class specification of DXIL Ops in DXIL.td (PR #87803)

[S. Bharadwaj Yadavalli via llvm-commits]

bharadwajy wrote:

Using separate fields to represent DXIL Op arguments and result types and not using DXIL Op classes to encapsulate them as function signatures - see https://github.com/llvm/llvm-project/pull/95807.

https://github.com/llvm/llvm-project/pull/87803