[llvm] [SPIRV] Add vector reduction instructions (PR #82786)

[Michal Paszkowski via llvm-commits]

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

Thank you for the patch and patience! LGTM! Confirming also that there are no OpenCL CTS regressions and no significant changes in the performance.

https://github.com/llvm/llvm-project/pull/82786