Reland "[LV] Print remark when loop cannot be vectorized due to invalid costs."

The original patch was:
  https://reviews.llvm.org/D105806

There were some issues with undeterministic behaviour of the sorting
function, which led to scalable-call.ll passing and/or failing. This
patch fixes the issue by numbering all instructions in the array first,
and using that number as the order, which should provide a consistent
ordering.

This reverts commit a607f641.