[clang] [clang][CodeGen][SPIR-V] Fix incorrect SYCL usage, implement missing interface (PR #109415)

[Alex Voicu via cfe-commits]

AlexVlx wrote:

> > > Are there any tests available to check this behavior?
> > 
> > 
> > The reworked tests do verify / rely on this behaviour, but I can add an individual test for both vanilla and AMDGCN flavoured SPIR-V, if that is preferred (might be better anyway).
> 
> Thanks @AlexVlx I will approve this change. You can add the tests as part of this PR or a follow-up PR. Either way is fine. Sincerely

Thank you for the review; I'll punt on adding targeted tests here because I *think* we'll have to add a few more of these queries, and I can just bundle specific tests there.

https://github.com/llvm/llvm-project/pull/109415