[llvm] [ValueTracking] Add support for `vector_reduce_{s, u}{min, max}` in `isKnownNonZero`/`computeKnownBits`. (PR #88169)

[via llvm-commits]

goldsteinn wrote:

 
> Yeah, I don't think we should do them if they require per-element reasoning to do something worthwhile. We can at least handle and/or though (and only in KnownBits).

Kk, ill post patches for the rest tomorrow.
Thinking a bit more we will be able to do a bit for most operators.

https://github.com/llvm/llvm-project/pull/88169