[llvm] [DirectX] Add `WaveActiveOp` builtin (PR #112058)

[Finn Plummer via llvm-commits]

inbelic wrote:

Okay, the design had been to use this intrinsic as the target of the intrinsic expansion for the intrinsics that would model the operations at a higher level. However, as creating this intrinsic also requires us to expose/suport it to the middle/front-end and the comment [here](https://github.com/llvm/llvm-project/pull/111884#discussion_r1803158872), then this approach to use an expansion is not the suitable solution.

https://github.com/llvm/llvm-project/pull/112058