[clang] [flang] [flang] add -floop-interchange and enable it with opt levels (PR #140182)

[KAWASHIMA Takahiro via cfe-commits]

kawashima-fj wrote:

I've confirmed the result of Fujitsu Compiler Test Suite. The only correctness issue affected by this commit is https://github.com/fujitsu/compiler-test-suite/blob/main/Fortran/0347/0347_0240.f, which will be resolved by #140709.

https://github.com/llvm/llvm-project/pull/140182