Add pattern to canonicalize for loop bounds

- add pattern to canonicalize affine.for loop bounds (using
  canonicalizeMapAndOperands)
- rename AffineForLoopBoundFolder -> AffineForLoopBoundFolder for
  consistency

Signed-off-by: Uday Bondhugula <uday@polymagelabs.com>

Closes tensorflow/mlir#111

COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/mlir/pull/111 from bondhugula:bound-canonicalize ee8fb7f43a7ffd45f6df3f53c95098d8b7e494c7
PiperOrigin-RevId: 269041220