This greatly simplifies the Point Distribute node. For a poisson disk
distribution, it now uses a simpler dart throwing variant. This results
in a slightly lower quality poisson disk distribution, but it still
fulfills our requirements: have a max density, minimum distance input
and stability while painting the density attribute.
This new implementation has a number of benefits over the old one:
* Much less and more readable code.
* Easier to extend with other distribution algorithms.
* Easier to transfer more attributes to the generated points later on.
* More predictable output when changing the max density and min distance.
* Works in 3d, so no projection on the xy plane is necessary.
This is related to T84640.
Differential Revision: https://developer.blender.org/D10104
d985751324