No way to express access chains with SPIR-V intrinsics.

I'm trying to make use of SPV_NV_raw_access_chains with SPIR-V intrinsics, but it does not seem like it's possible to do this.

The complicated part is that `OpRawAccessChainNV` returns a pointer, just like any other access chain, but it does not seem possible to return spirv_by_reference, so I'm a bit stumped. Is there any way to express plain OpAccessChain as-is with SPIR-V intrinsics in the first place? That'd be a good place to start.

No files or tests are named. Start by locating the SPIR-V intrinsic handling for OpAccessChain and the representation of spirv_by_reference, then investigate how OpRawAccessChainNV's pointer result could be expressed; done means a supported way to represent access chains with SPIR-V intrinsics, covered by focused tests.

Written by the indexing model from the issue text.