ifcdiff: fix crash when exporting property diffs to JSON

DeepDiff's dictionary_item_added/set_item_added results are a
deepdiff.helper.SetOrdered instance, which subclasses orderly_set's
StableSetEq rather than the OrderedSet class json_dump_default checked
for, so the property relationship check always crashed export() with
"Object of type SetOrdered is not JSON serializable". Check against
StableSet, the common base class shared by every orderly_set set
flavour, instead.

Fixes #8905

Generated with the assistance of an AI coding tool.

(cherry picked from commit fbe36532a0)

src/ifcdiff/ifcdiff.py

@@ -36,7 +36,7 @@ import ifcopenshell.util.representation
 import ifcopenshell.util.selector
 import numpy as np
 from deepdiff import DeepDiff
-from orderly_set import OrderedSet
+from orderly_set import StableSet
 
 __version__ = version = "0.0.0"
 
@@ -257,7 +257,7 @@ class IfcDiff:
 
     def json_dump_default(self, obj):
         # result of DeepDiff may contain ordered sets
-        if isinstance(obj, (OrderedSet, set)):
+        if isinstance(obj, (StableSet, set)):
             return list(obj)
         return json.JSONEncoder.default(None, obj)