[MLIR] Add affine.parallel folder and normalizer

Add a folder to the affine.parallel op so that loop bounds expressions are canonicalized.

Additionally, a new AffineParallelNormalizePass is added to adjust affine.parallel ops so that the lower bound is always 0 and the upper bound always represents a range with a step size of 1.

Differential Revision: https://reviews.llvm.org/D84998