unroll and jam: fix order of jammed bodies

- bodies would earlier appear in the order (i, i+3, i+2, i+1) instead of
  (i, i+1, i+2, i+3) for example for factor 4.

- clean up hardcoded test cases

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

Closes tensorflow/mlir#170

COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/mlir/pull/170 from bondhugula:ujam b66b405b2b1894a03b376952e32a9d0292042665
PiperOrigin-RevId: 273613131