Optimize `ScaleValue` for special factors

As shown in #7402, special factors for `ScaleValue` like scaling by `-1` can be pretty significantly optimized because for negation boundary checks can be done by a single equality check instead of two inequalities. `ScaleValue` can handle these special factors like `-1` differently and give cheaper cost. Cost model should be able to have different "branches" for different coefficient(or so was I told, @kwxm can you confirm here?).

Also check factors like `2`. `x + x` might be cheaper than `2 * x`.