[NFC][LoopInterchange] Explicitly pass both `InnerLoop` and `OuterLoop` to `processLoop`

This is a split patch of D96644.

Explicitly pass both `InnerLoop` and `OuterLoop` to function `processLoop` to remove the need to swap elements in loop list and allow making loop list an `ArrayRef`.
Also, fix inconsistent spellings of `OuterLoopId` and `Inner Loop Id` in debug log.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D96650