[NFCI] SCEVExpander: emit intrinsics for integral {u,s}{min,max} SCEV expressions

These intrinsics, not the icmp+select are the canonical form nowadays,
so we might as well directly emit them.

This should not cause any regressions, but if it does,
then then they would needed to be fixed regardless.

Note that this doesn't deal with `SCEVExpander::isHighCostExpansion()`,
but that is a pessimization, not a correctness issue.

Additionally, the non-intrinsic form has issues with undef,
see https://reviews.llvm.org/D88287#2587863