[llvm] [SPIR-V] Add implementation of G_SPLAT_VECTOR opcode and fix invalid types processing (PR #84766)

[Michal Paszkowski via llvm-commits]

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

Thank you for the patch! LGTM! No more regressions after most recent commit!

https://github.com/llvm/llvm-project/pull/84766