Implement a volume to mesh node based on T84605.
Contrary to the Volume to Mesh modifier, this node does not have a smooth shading option. This should probably be handled by a separate node.
The actual volume-to-mesh code is shared with the corresponding modifier. To make that possible I extracted the code into a new file in blenkernel.
As of right now, the node can only work with volumes generated by the Points to Volume node. This limitation will be lifted soonish. This is related to T85159.