[llvm] [DXIL] Define and generate `DXILAttribute` and `DXILProperty` (PR #117072)

[Finn Plummer via llvm-commits]

inbelic wrote:

Created an issue to track the additional work of verifying the current attributes specified in DXC: https://github.com/llvm/llvm-project/issues/123825

https://github.com/llvm/llvm-project/pull/117072