Use SPV_EXT_long_vector extension for non-standard vector size (#3777)
For a vector type, add `SPV_EXT_long_vector` extension and prioritize it
over `SPV_INTEL_vector_compute` whenever the vector type doesn't have a
standard component size (2, 3, 4, 8, or 16).
Original commit:
https://github.com/KhronosGroup/SPIRV-LLVM-Translator/commit/7d4b128df7e6ff3