Refactor tests and remove unused imports

- Cleaned up test files by removing unnecessary imports and unused parameters.
- Simplified test functions by eliminating redundant parameterization and consolidating logic.
- Updated test cases to directly use defined values instead of parameterized inputs where applicable.
- Enhanced readability and maintainability of the test code across various test files.

tests/tools/nodes/test_normal_scale.py

@@ -7,7 +7,6 @@ from anyimage.operators.cutout_tool.shape import NORMAL_REDUCTION_ATTRIBUTE_NAME
 from tests.support.materials import image_layer
 
 
-@pytest.mark.parametrize('image_layer', ['definition', 'asset'], indirect=True)
 @pytest.mark.parametrize('engine', ['CYCLES', 'BLENDER_EEVEE_NEXT'])
 @pytest.mark.parametrize('domain', ['POINT', 'FACE'])
 def test_normal_scale_preserves_missing_and_zero_weights(image_layer, engine, domain, tmp_path):