Blender Git Loki

Geometry Nodes: use GeometrySet when evaluating pointcloud modifiers

This changes the signature of the modifyPointCloud function.
I'm doing that instead of making a new callback, because it requires
changes to significantly fewer files. Eventually it would be good
combine modifyMesh, modifyHair, modifyPointCloud and modifyVolume
into one modifyGeometrySet.

I temporarily disabled the displacement only modifiers for point clouds.
Support can be added back a bit later. I assume those have not been
used anywhere anyway.

The output of point cloud modifiers can not only be another point cloud,
but also a mesh and/or some instances. I added a new geometry_set_eval
field to Object_Runtime. For point cloud objects, the final geometry is
now referenced by that pointer instead of data_eval. The data_eval field
is still initialized after modifier evaluation to make some other code happy.

The evaluated geometry set is not yet passed to the renderer, so a point
cloud is currently rendered empty.