Refactor and enhance geometry node groups for depth plane and material layers

- Updated the depth plane node group to load from an asset and simplified the interface.
- Created a new build script for depth plane geometry nodes.
- Introduced material layer groups for image and depth materials with appropriate sockets.
- Added functionality to connect balloon normal scale to the image material.
- Enhanced tests to validate the new node groups and their connections.
- Ensured that production code does not create node groups directly.

tools/node_assets/build.py

@@ -17,6 +17,8 @@ from build_cutout import (
     build_cutout_modifier_group,
     build_node_group,
 )
+from build_depth_plane import build_depth_plane_group
+from build_material_layers import build_material_layer_group
 from build_mesh_plane import build_mesh_plane_group
 from build_shadeless import build_shadeless_group
 OUTPUT_PATH = (
@@ -31,7 +33,10 @@ OUTPUT_PATH = (
 def main():
     bpy.ops.wm.read_factory_settings(use_empty=True)
     bpy.context.preferences.filepaths.save_version = 0
-    build_mesh_plane_group()
+    mesh_plane = build_mesh_plane_group()
+    build_depth_plane_group(mesh_plane)
+    build_material_layer_group()
+    build_material_layer_group(depth_plane=True)
     build_shadeless_group()
     shape_groups = {
         shape: build_node_group(shape)