[HLSL] vector<->array conversions are allowed as inout parameters if explicitly casted

[spall]

This is allowed in DXC:
vector<->array conversions where we can create a cxvalue, but only from an explicit cast:
https://godbolt.org/z/ezzjj6dWo
but in clang produces the following error
cannot bind non-lvalue argument (float4)V to inout paramemter

[spall]

Blocked on design discussion