[llvm] [LV] Emit better debug and opt-report messages when vectorization is disallowed in the LoopVectorizer (PR #158513)

[Tibor Győri via llvm-commits]

TiborGY wrote:

> Is this patch NFC? If this is NFC, please mark NFC in the commit title; If not, could you add a test case to show the improvement?

Thanks for the comment, I will be adding test cases soon (probably next few days)

https://github.com/llvm/llvm-project/pull/158513