* [ARITH] Introduce iterator (quasi)affine map detection.
The loop transformations (split, fuse) create bijective
maps from a collection of source iterators to target iterators.
DetectIterMap is a function that detects such bijective mappings
from the lowered index expression.
We choose the term quasi affine to be consistent with the
terminology used by in polyhedral compilation.
DetectIterMap can handle symbolic integers(in split/fuse) to some extent.
The utility can be useful in detecting loop transformation
patterns and data layout change patterns in TIR.
* Update per feedback
Tianqi Chen
60ed926105