[mlir][transform] Update transform.loop.peel (reland #67482)

This patch updates `transform.loop.peel` so that this Op returns two
rather than one handle:
  * one for the peeled loop, and
  * one for the remainder loop.
Also, following this change this Op will fail if peeling fails. This is
consistent with other similar Ops that also fail if no transformation
takes place.

Relands #67482 with an extra fix for transform_loop_ext.py