[llvm] [Arch64][SVE] Lower svrev_* to llvm.vector.reverse and fold svrev(svrev(x)) -> x (PR #116422)

[Jorge Botto via llvm-commits]

jf-botto wrote:

> I'm seeing some odd things in the code, the accompanying test doesn't pass, and some of the previous review comments are not yet addressed, so it's not really clear to me if you intended this PR to be ready for another round of review?

I'm still working on a few things, shouldn't have pushed. I need a little bit more time before a review, apologies.

https://github.com/llvm/llvm-project/pull/116422