GPv3: Line Art Modifier

This is a migration of the current Line Art modifier to GPv3.

Note:
- The modifier is using the exact same DNA structure as the old one, it's re-defined in a different name. At the moment all the variable names and placement after the `ModifierData` part should stay exactly the same until we do proper versioning of the modifier data and completely remove the GPv2 support.
- Vertex weight transfer feature no longer supports name initial matching ("group" used to match "group1","group2" etc). Now it will only transfer vertex weight from source vertex groups that has the exact same name as specified.

Pull Request: https://projects.blender.org/blender/blender/pulls/117028

scripts/startup/bl_ui/properties_data_modifier.py

@@ -159,6 +159,7 @@ class OBJECT_MT_modifier_add_generate(ModifierAddMenu, Menu):
             self.operator_modifier_add(layout, 'GREASE_PENCIL_MIRROR')
             self.operator_modifier_add(layout, 'GREASE_PENCIL_MULTIPLY')
             self.operator_modifier_add(layout, 'GREASE_PENCIL_SUBDIV')
+            self.operator_modifier_add(layout, 'LINEART')
         layout.template_modifier_asset_menu_items(catalog_path=self.bl_label)