[llvm] [LoopInterchange] Don't rely on ASSERTS build for tests. NFC. (PR #116780)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

I will precommit this change soon, adding you as reviewers as a FYI, as I think this is just a NFC reshuffle of tests that increases test coverage; and no (fundamental) changes have been made to the tests itself, just the CHECKing. 

https://github.com/llvm/llvm-project/pull/116780