feat(selection): separate selection geometry from image content processing

- Introduced a new design for selection rasterization that decouples the selection geometry from the image content, ensuring that the SelectionMask is independent of the source image's alpha and color.
- Updated the `rasterize_selection_path` function to only accept selection paths and image dimensions, removing parameters related to source alpha and alpha thresholds.
- Implemented a new approach for handling selection paths using non-zero winding fill, ensuring overlapping areas are preserved.
- Enhanced performance by utilizing a scanline algorithm for rasterization, significantly reducing processing time for high-resolution images.
- Updated internal documentation and added comprehensive tests to validate the new behavior and performance improvements.
- Ensured backward compatibility by maintaining existing interfaces where necessary while introducing breaking changes in the selection processing logic.

tests/test_server_runtime.py

@@ -691,6 +691,7 @@ class ServerRuntimeTest(unittest.TestCase):
                 normal_mode="OBJECT",
             )
 
+        infer.assert_called_once()
         self.assertEqual(
             set(result),
             {"vector_depth", "depth_metadata", "object_normal"},
@@ -749,7 +750,7 @@ class ServerRuntimeTest(unittest.TestCase):
             normal_mode="OBJECT",
         )
 
-    def test_generate_cutout_artifacts_refine_an_already_rasterized_selection(self):
+    def test_generate_cutout_artifacts_refines_the_bounds_image(self):
         job = sys.modules["server.jobs.cutout"]
         input_path = self.storage_root / "input.png"
         input_path.write_bytes(b"selection")