[next] Can we invert the draw paths?

[chrisbanes]

Currently Haze is all smoke and mirrors, as it draws all of the blurred areas in the haze layout node. The hazeChild nodes just update the size, shape, etc, which the haze modifier reads, to know where to draw.

What if we invert this, so that the haze node creates a graphics layer and puts it in the HazeState. Each hazeChild then uses that graphics layer to apply the blurred effect locally in the relevant layout node.

This could fix a number of issues, including #213, #229 and #245, which all boil down to the fact that we don't draw in the child nodes.

Even if this works, there is a downside though: anything which draws in-between the haze and hazeChild would be ignored. This is because the children are directly drawing the haze parent.

I see two options to workaround this:

1. Easy: make this 'mode' optional.
2. Harder: We add a hazeAncestor modifier which devs have to apply to intermediary ancestors. This modifier will basically do the same thing as haze and stuff a graphics layer into the HazeState. The hazeChild would then draw all of the ancestor layers in the effect.

Option 2 is out of scope for the initial release, but can be followed up on. Again, even if this works.