[InstCombine] move add after min/max intrinsic

This is another regression noted with the proposal to canonicalize
to the min/max intrinsics in D98152.

Here are Alive2 attempts to show correctness without specifying
exact constants:
https://alive2.llvm.org/ce/z/bvfCwh (smax)
https://alive2.llvm.org/ce/z/of7eqy (smin)
https://alive2.llvm.org/ce/z/2Xtxoh (umax)
https://alive2.llvm.org/ce/z/Rm4Ad8 (umin)
(if you comment out the assume and/or no-wrap, you should see failures)

The different output for the umin test is due to a fold added with
c4fc2cb5 :

// umin(x, 1) == zext(x != 0)

We probably want to adjust that, so it applies more generally
(umax --> sext or patterns where we can fold to select-of-constants).
Some folds that were ok when starting with cmp+select may increase
instruction count for the equivalent intrinsic, so we have to decide
if it's worth altering a min/max.

Differential Revision: https://reviews.llvm.org/D110038