[Hexagon] Add support for ISD::SMAX/SMIN/UMAX/UMIN instead of custom dag patterns

This should handle the basic integer min/max handling - the HVX ops are still TODO.

This is some necessary cleanup work for min/max ops to eventually help us move the add/sub sat patterns into DAGCombine - D91876.

Differential Revision: https://reviews.llvm.org/D92112