[llvm] Add support for SPIR-V extension: SPV_INTEL_function_pointers (PR #80759)

[Vyacheslav Levytskyy via llvm-commits]

VyacheslavLevytskyy wrote:

@michalpaszkowski I simplified implementation by removing the feature of resolving opaque pointer types by information about indirect calls. I think it's better to address this later, as just one of many cases when we'd benefit from a more general scheme of improvement of resolving opaque pointer types. This subject appears time from time and probably deserves a generalized solution.

https://github.com/llvm/llvm-project/pull/80759