[llvm] [DirectX] Add `DXILRefineTypesPass` to prevent type promotion (PR #169384)

[Finn Plummer via llvm-commits]

inbelic wrote:

>From offline discussion with @bogner it looks like we can try to infer the type directly in the `SimplifyAnyMemTransfer` of `InstCombine`.

It appears that just inferring from the `alloca` will be sufficient for our case as we don't need to check any dxil specific intrinsics. This will also positively impact the general instcombine pass as well!

I will open up a pr with reference to this one for context.

https://github.com/llvm/llvm-project/pull/169384