[mlir][Affine] Remove single iteration affine.for ops in AffineLoopNormalize

This patch renames AffineParallelNormalize to AffineLoopNormalize to make it
more generic and be able to hold more loop normalization transformations in
the future for affine.for and affine.parallel ops. Eventually, it could also be
extended to support scf.for and scf.parallel. As a starting point for affine.for,
the patch also adds support for removing single iteration affine.for ops to the
the pass.

Differential Revision: https://reviews.llvm.org/D90267