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

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

> > Has #116144 (correctness issue) been addressed?
> 
> It would have been fixed with #119345 . As far as I know, there are no known correctness issues on the LoopInterchange side.

Correct, should have been fixed. 
In addition, I have just closed the following bug reports that had the same underlying issue as that one:
- https://github.com/llvm/llvm-project/issues/46867
- https://github.com/llvm/llvm-project/issues/47259
- https://github.com/llvm/llvm-project/issues/47401



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