Introduce a new BinaryOp to commonize simple binary ops, introduce traits for

ResultIsFloatLike/ResultIsIntegerLike, move some code out of templates into
shared code, keep the ops in StandardOps.cpp/h sorted.

This significantly reduces the boilerplate for Add/Mul sorts of ops.  In a subsequent patch, I plan to rename OpBase to Op, but didn't want to clutter this diff.

PiperOrigin-RevId: 214622871