Grease Pencil armature deformation has to use the correct
`vertex_group_names` list from the `Curves` (i.e. drawings) rather than
the names from its parent `GreasePencil` data block.
The ancient armature deformation code used a `defbase` list (`ListBase`
of type `bDeformGroup`) from the object via `BKE_id_defgroup_list_get`.
This function does not have enough information to determine the correct
vertex groups for GPv3, and it's use inside supposedly generic code is
highly questionable.
This patch removes the `defbase` lookup inside
`armature_deform_coords_impl` and instead passes an explicit list of
vertex group names to be used for resolving indices. We already have
context in every place this is called to determine the correct vertex
groups, without having to make assumptions down the line based on just
the object type.
Pull Request: https://projects.blender.org/blender/blender/pulls/127509
49965841bb