Tests: Add Cycles test for transparent spatial splitting artifacts

With the HIPRT backend for Cycles, rays can end up hitting the same
triangle multiple times due to a issue in the spatial splitting
algorithm.

Most of the time this issue isn't visible, but it is quite obvious in
semi-transparent shadows of meshes.

So this commit adds a file that contains a object made up of many
semi-transparent rectangular prisms casting a shadow onto the a plane.

Ref: blender/blender#117527
Ref: blender/blender-test-data!76

tests/python/storm_render_tests.py

@@ -43,6 +43,7 @@ BLOCKLIST_METAL = [
     "light_path_is_transmission_ray.blend",
     "light_path_ray_depth.blend",
     "light_path_ray_length.blend",
+    "transparent_spatial_splits.blend",
     # Volume
     "light_link_surface_in_volume.blend",
     "openvdb.*.blend",