[llvm] [LoopInterchange] Enable it by default (WIP) (PR #124911)

[Michael Kruse via llvm-commits]

Meinersbur wrote:

Could you provide numbers for performance changes (improvments and regressions), e.g. highlights from llvm-test-suite? Would help illustrating that we also gain something from slighlty increased compile-time.

https://github.com/llvm/llvm-project/pull/124911