bpo-40521: Fix update_slot() when INTERN_NAME_STRINGS is not defined (#20246)

Fix type update_slot() function when the macro INTERN_NAME_STRINGS is
not defined: use _PyUnicode_EQ() in this case.

Author: vstinner

Objects/typeobject.c

@@ -7661,8 +7661,17 @@ update_slot(PyTypeObject *type, PyObject *name)
     assert(slotdefs_initialized);
     pp = ptrs;
     for (p = slotdefs; p->name; p++) {
-        if (p->name_strobj == name)
+        assert(PyUnicode_CheckExact(p->name_strobj));
+        assert(PyUnicode_CheckExact(name));
+#ifdef INTERN_NAME_STRINGS
+        if (p->name_strobj == name) {
+            *pp++ = p;
+        }
+#else
+        if (p->name_strobj == name || _PyUnicode_EQ(p->name_strobj, name)) {
             *pp++ = p;
+        }
+#endif
     }
     *pp = NULL;
     for (pp = ptrs; *pp; pp++) {