[FIX] orm: patch manual field names

The check for manual field names moved from being
a model method to a util function. It needs to be
patched starting version saas~18.4 to allow loading
custom module fields as manual for tests during the
upgrade process.

odoo/odoo#224524
odoo/enterprise#93335

Author: jjmaksoud

src/util/orm.py

@@ -726,8 +726,11 @@ def _add_magic_fields(self):
 
         patches.append(patch.object(BaseModel, "_add_magic_fields", _add_magic_fields))
 
-    if version_gte("saas~16.4"):
-        # 3.5.3 allow loading manual fields
+    # 3.5.3 allow loading manual fields
+    if version_gte("saas~18.4"):
+        patches.append(patch("odoo.fields.is_manual_field_name", lambda name: True))
+        patches.append(patch("odoo.orm.model_classes.is_manual_field_name", lambda name: True))
+    elif version_gte("saas~16.4"):
         patches.append(patch("odoo.addons.base.models.ir_model.IrModelFields._is_manual_name", lambda self, name: True))
 
     with all_patches():