[HLSL] Add __builtin_hlsl_create_handle

This is pretty straightforward, it just adds a builtin to return a
pointer to a resource handle. This maps to a dx intrinsic.

The shape of this builtin and the underlying intrinsic will likely
shift a bit as this implementation becomes more feature complete, but
this is a good basis to get started.

Depends on D128569.

Differential Revision: https://reviews.llvm.org/D130016