Openapi schema gen preserve order of field remap

During field remapping stage of openapi schema generation the order of
iteration is not consistent across runs. This leads to non-deterministic
schema generation

Preserve the order of this iteration across runs by sorting by the
"new_name", i.e. the value inserted in this mapping

fastapi/_compat/v2.py

@@ -302,7 +302,10 @@ def _remap_definitions_and_field_mappings(
     Dict[str, Any],
 ]:
     old_name_to_new_name_map = {}
-    for field_key, schema in field_mapping.items():
+    for field_key, schema in sorted(
+        field_mapping.items(),
+        key=lambda x: model_name_map.get(x[0][0].type_),
+    ):
         model = field_key[0].type_
         if model not in model_name_map:
             continue