[llvm] [DXContainer] Update DXContainer to match D3D12 spec (PR #143201)

[Finn Plummer via llvm-commits]

================
@@ -78,7 +78,6 @@ ROOT_ELEMENT_FLAG(11, SamplerHeapDirectlyIndexed)
 // ROOT_DESCRIPTOR_FLAG(bit offset for the flag, name).
 #ifdef ROOT_DESCRIPTOR_FLAG
 
-ROOT_DESCRIPTOR_FLAG(0, NONE)
----------------
inbelic wrote:

We should probably be consistent with this and `ROOT_DESCRIPTOR_FLAG` (this is just a subset).

Can we agree that all flag values have the direct hex value as opposed to any shift? And enums should have their incremented integer values.

I would strongly prefer to have the `None` enum for when I re-use these values on the frontend.

https://github.com/llvm/llvm-project/pull/143201