[llvm] [DirectX backend] emits metadata for DXIL version. (PR #88350)

[Justin Bogner via llvm-commits]

https://github.com/bogner commented:

If the fact that this is missing is blocking something then it's probably fine to do it like this for now, but as implied by #66015 and #66016 we'll presumably need to revisit this as we evolve our story around DXIL metadata abstractions.

In any case, it's probably worth considering @thegreatbeanz's point about separating the abstraction of DXIL version from the shader model. It'll be much easier to decouple these if we design that early rather than if we bake in assumptions like this in the short term.

https://github.com/llvm/llvm-project/pull/88350