Combine "layer visuals affecting" views

[helje5]

As mentioned in: #40

We currently have the issue that visual affecting views do not modify a single div, but result in multiple divs. So this:

      Text("🥑🍞")
        .padding(.all)
        .background(.green, cornerRadius: 12)
        .shadow(color: .lightGray, radius: 5, x: 2, y: 2)

Results in:

I think the solution is to have .background, .shadow and the likes return a single "Style patching tree node".

Important: Layout nodes like .padding or .frame are different! They need to result in new divs because the ordering matters (or maybe they can combine if the ordering would lead to the same result). The old:

      Text("🥑🍞")
        .padding(.all)
        .background(.green, cornerRadius: 12)

      Text("🥑🍞")
        .background(.green, cornerRadius: 12)
        .padding(.all)