Affine expression analysis and simplification.

Outside of IR/
- simplify a MutableAffineMap by flattening the affine expressions
- add a simplify affine expression pass that uses this analysis
- update the FlatAffineConstraints API (to be used in the next CL)

In IR:
- add isMultipleOf and getKnownGCD for AffineExpr, and make the in-IR
  simplication of simplifyMod simpler and more powerful.
- rename the AffineExpr visitor methods to distinguish b/w visiting and
  walking, and to simplify API names based on context.

The next CL will use some of these for the loop unrolling/unroll-jam to make
the detection for the need of cleanup loop powerful/non-trivial.

A future CL will finally move this simplification to FlatAffineConstraints to
make it more powerful. For eg., currently, even if a mod expr appearing in a
part of the expression tree can't be simplified, the whole thing won't be
simplified.

PiperOrigin-RevId: 211012256
diff --git a/include/mlir/Analysis/HyperRectangularSet.h b/include/mlir/Analysis/HyperRectangularSet.h
index ba28b3e..8956aeb 100644
--- a/include/mlir/Analysis/HyperRectangularSet.h
+++ b/include/mlir/Analysis/HyperRectangularSet.h
@@ -95,6 +95,7 @@
   HyperRectangularSet(unsigned numDims, unsigned numSymbols,
                       ArrayRef<ArrayRef<AffineExpr *>> lbs,
                       ArrayRef<ArrayRef<AffineExpr *>> ubs,
+                      MLIRContext *context,
                       IntegerSet *symbolContext = nullptr);
 
   unsigned getNumDims() const { return numDims; }