ESIMD W/A Feature Check Guard (#3759)
This is a follow-up to #3689
The original workaround (#3476) applied unconditionally, accepting
invalid SPIR-V (`OpConvertPtrToU` applied to target extension types) in
all contexts.
This PR gates that W/A on `SPV_INTEL_vector_compute` - to limit
acceptance of spec-violating SPIR-V to the ESIMD use case that actually
needs it.
Original commit:
https://github.com/KhronosGroup/SPIRV-LLVM-Translator/commit/9f48169a8846a68
