Implement SPV_KHR_poison_freeze extension (#3751)
Spec is available here:
https://github.com/KhronosGroup/SPIRV-Registry/blob/main/extensions/KHR/SPV_KHR_poison_freeze.asciidoc
Original commit:
https://github.com/KhronosGroup/SPIRV-LLVM-Translator/commit/cfecbadc2d0248e
