[llvm] [FixIrreducible][UnifyLoopExits] Support switch statements (PR #206567)

[via llvm-commits]

hertelukas wrote:

Done, thanks for the review. I also changed the `FixIrreducible/switch.ll` test, as the order of the cycles has changed when printing, so I removed the `CYCLES-*` test.s

https://github.com/llvm/llvm-project/pull/206567