[Reassociate] replace fake binop queries with 'match' API

We need to update this code before introducing an 'fneg' instruction in IR,
so we might as well kill off the integer neg/not queries too.

This is no-functional-change-intended for scalar code and most vector code. 
For vectors, we can see that the 'match' API allows for undef elements in 
constants, so we optimize those cases better.

Ideally, there would be a test for each code diff, but I don't see evidence
of that for the existing code, so I didn't try very hard to come up with new 
vector tests for each code change.

Differential Revision: https://reviews.llvm.org/D53533

llvm-svn: 345042