vkd3d-shader/hlsl: Implement simplification of associative and commutative binary expressions.

The simplification process applies the following rewrite rules, if OP is associative:

  (x OP y) OP z -> x OP (y OP z), if (y OP z) simplifies
  x OP (y OP z) -> (x OP y) OP z, if (x OP y) simplifies

And the following rewrite rule, if OP is commutative, c is a constant, and x is a non-constant:

  c OP x -> x OP c

For example, the following HLSL

uint x;
float4 main() : sv_target
{
    return 3 + (4 * x * 5) - 6 + 7;
}

gets simplified to

2:       uint | x[0c]
3:       uint | 20 
4:       uint | * (@2 @3 )
5:       uint | 4 
6:       uint | + (@4 @5 )
7:      float | cast (@6 )
8:     float4 | @7.xxxx
9:            | = (<output-sv_target0>[0c] @8)