Geometry Nodes: Parallel Edges to Face Groups

This loop might be 7x faster (not whole node).
All other code is already parallel, not sure why this was disabled.
Potentially, this was missed after some cleanup.

Pull Request: https://projects.blender.org/blender/blender/pulls/115246

source/blender/nodes/geometry/nodes/node_geo_edges_to_face_groups.cc

@@ -61,7 +61,7 @@ class FaceSetFromBoundariesInput final : public bke::MeshFieldInput {
 
     AtomicDisjointSet islands(faces.size());
     non_boundary_edges.foreach_index(
-        [&](const int edge) { join_indices(islands, edge_to_face_map[edge]); });
+        GrainSize(2048), [&](const int edge) { join_indices(islands, edge_to_face_map[edge]); });
 
     Array<int> output(faces.size());
     islands.calc_reduced_ids(output);