[InstCombine] Extend 'shift with constants' vector tests

Added missing test coverage for shl(add(and(lshr(x,c1),c2),y),c1) -> add(and(x,c2<<c1),shl(y,c1)) combine

Rename tests as 'foo' and 'bar' isn't very extensible

Added vector tests with undefs and nonuniform constants