[llvm] [LoadStoreVectorizer] Postprocess and merge equivalence classes (PR #114501)

[Michal Paszkowski via llvm-commits]

https://github.com/michalpaszkowski requested changes to this pull request.

@v-klochkov Thank you for adding the test and addressing the comments! I just ran the code formatter. One more thing, could you please name the unnamed/numbered vregs in the test -- this should help with any changes in the future? Please rebase on top of `main` branch -- once the builbots pass, I will merge the change.

https://github.com/llvm/llvm-project/pull/114501