[mlir][transform] Fix crash when op is erased during transform.foreach (#66357)

Fixes a crash when an op, that is mapped to handle that a
`transform.foreach` iterates over, was erased (through the
`TrackingRewriter`). Erasing an op removes it from all mappings and
invalidates iterators. This is already taken care of when an op is
iterating over payload ops in its `apply` method, but not when another
transform op is erasing a tracked payload op.