Enable command list reuse for Xbox (#13173)
Removes the workaround introduced in #12063, which disabled DML command
list reuse for Xbox builds.
The ID3D12CommandList created in FusedGraphKernel takes points to an
ID3D12CommandAllocator that is local to the `BuildReusableCommandList`
function. On PC it would seem the command list is keeping the command
allocator alive, but this is highly suspect logic that definitely
doesn't work on Xbox. I find no documentation indicating this logic
should work (a section on [reference
counting](https://learn.microsoft.com/en-us/windows/win32/direct3d12/recording-command-lists-and-bundles#reference-counting)
makes it clear command lists take no refs on D3D objects passed as args
to its APIs; however, it's unclear if this also applies to its
construction).
A second (small) change is constructing the command list straight into
`ID3D12GraphicsCommandList` and removing an unnecessary QI.
