Fix: Geometry Nodes: wrong anonymous attribute lifetimes with fields in geometry bundles

This fixes missing anonymous attributes when a reference to them is
stored in a geometry bundle.

A regression test that checks for this has been added (it breaks without
this change).

Pull Request: https://projects.blender.org/blender/blender/pulls/159149

tests/python/geo_node_test.py

@@ -5,10 +5,18 @@
 
 import os
 import sys
+import bpy
 
 sys.path.append(os.path.dirname(os.path.realpath(__file__)))
 from modules.mesh_test import BlendFileTest
 
+if "bake_anonymous_attribute_reference" in bpy.data.filepath:
+    if bpy.app.version_cycle == "alpha":
+        bpy.context.preferences.experimental.use_geometry_bundle = True
+    else:
+        print("Skipped because bundles and closures are still experimental.")
+        sys.exit(0)
+
 geo_node_test = BlendFileTest("test_object", "expected_object", threshold=1e-4)
 result = geo_node_test.run_test()