Enhance image editing tests and functionality

- Added parameterized tests for image edit replacement to ensure alpha mode preservation.
- Refactored existing tests to utilize new image editing methods and improve clarity.
- Introduced new tests for image target functionality, ensuring proper handling of shared textures and context.
- Updated various tests to validate alpha mode handling across different scenarios.
- Improved undo/redo functionality in image operators to maintain state consistency.
- Added support for texture node actions, enhancing integration with Blender's node system.
- Ensured that image properties are preserved during operations and that invalid contexts are handled gracefully.

tests/support/blender.py

@@ -78,12 +78,17 @@ class BlenderTestCase(unittest.TestCase):
                 prepend=lambda draw: cls.outliner_menu_draws.insert(0, draw),
                 remove=lambda draw: cls.outliner_menu_draws.remove(draw),
             ),
+            NODE_MT_context_menu=SimpleNamespace(
+                prepend=lambda draw: cls.node_menu_draws.insert(0, draw),
+                remove=lambda draw: cls.node_menu_draws.remove(draw),
+            ),
         )
         cls.registered = []
         cls.registered_tools = []
         cls.status_bar_draws = []
         cls.context_menu_draws = []
         cls.outliner_menu_draws = []
+        cls.node_menu_draws = []
         fake_bpy.utils = SimpleNamespace(
             register_class=cls.registered.append,
             unregister_class=cls.registered.remove,
@@ -177,6 +182,7 @@ class BlenderTestCase(unittest.TestCase):
         self.status_bar_draws.clear()
         self.context_menu_draws.clear()
         self.outliner_menu_draws.clear()
+        self.node_menu_draws.clear()
         self.fake_bpy.data = SimpleNamespace(
             objects=SimpleNamespace(get=lambda _name: None),
         )