[llvm] [SPIR-V] Support `SPV_INTEL_int4` extension (PR #141031)

[Michal Paszkowski via llvm-commits]

https://github.com/michalpaszkowski approved this pull request.

LGTM! Thanks for working on this! I will wait for the GitHub workflows to finish running and then can merge the PR.

https://github.com/llvm/llvm-project/pull/141031