Add tests and implement boundary smoothing and cutout functionality

- Introduced tests for boundary smoothing in `test_boundary_smoothing.py`, verifying that smoothing reduces stair-step artifacts while preserving boundary integrity.
- Added tests for cutout boundary behavior in `test_cutout_boundary.py`, ensuring proper handling of boundary triangles and normal blending.
- Created `test_temporary_attributes.py` to check the cleanup of temporary attributes across depth modifier branches, ensuring no warnings are raised.
- Implemented point culling functionality in `test_validity.py`, confirming that invalid points are removed without affecting adjacent geometry.
- Developed boundary smoothing logic in `boundary_smoothing.py`, allowing for depth smoothing while maintaining edge integrity.
- Added cutout boundary management in `cutout_boundary.py`, including functions for removing boundary triangles and tapering thickness profiles.
- Implemented validity checks in `validity.py` to ensure proper deletion of invalid vertices and associated wire edges.

tests/anyimage/operators/test_cutout_geometry.py

@@ -46,7 +46,8 @@ def test_cutout_node_groups_are_loaded_from_the_asset():
     ) as load:
         for shape in cutout_shape.CUTOUT_NODE_GROUP_NAMES:
             assert cutout_object.load_cutout_node_group(shape) is loaded
-            load.assert_called_with(cutout_shape.CUTOUT_NODE_GROUP_NAMES[shape], asset_revision=11)
+            load.assert_called_with(cutout_shape.CUTOUT_NODE_GROUP_NAMES[shape],
+                                    asset_revision=18 if shape == "DEPTH_SOLID" else 11)
         assert load.call_count == 4