[clang] [llvm] [DirectX] Set DXIL Version using shader model version in compilation target profile (PR #89823)

[Justin Bogner via cfe-commits]

https://github.com/bogner requested changes to this pull request.

There's a lot of churn here so I'm not 100% sure I saw all of the real changes, but I think I got them all. It might be nice to move the NFC parts into their own commit (if we actually need them, see my other comments).

I don't think we should treat the DXIL architecture differently than all of the other architectures in LLVM like this. More on that in the comments.

https://github.com/llvm/llvm-project/pull/89823