This adds a "Group ID" input to the Fill Curve node, per #102285.
The curve filling operation is performed separately for each group,
so curves associated with different Group IDs do not intersect.
This implementation also supports Grease Pencil 3 curves.
Co-authored-by: Hans Goudey <hans@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/114048