[clang] [flang] [Clang][Flang] Enable loop interchange by default at >O1 opt levels (PR #216920)

[Madhur Amilkanthwar via cfe-commits]

madhur13490 wrote:

Thanks all the kind review. I am doing some testing and will get this in soon. 

https://github.com/llvm/llvm-project/pull/216920