Add helper function get_ob_size

Author: fangerer

graalpython/com.oracle.graal.python.cext/src/capi.c

@@ -429,6 +429,7 @@ PyAPI_FUNC(RESULT) get_##NAME(RECEIVER obj) {                      \
 
 TYPE_FIELD_GETTER(PyObject*, ob_type)
 PRIMITIVE_FIELD_GETTER(PyObject*, Py_ssize_t, ob_refcnt)
+PRIMITIVE_FIELD_GETTER(PyVarObject*, Py_ssize_t, ob_size)
 OBJECT_FIELD_GETTER(PyTypeObject*, tp_dict)
 OBJECT_FIELD_GETTER(PyTypeObject*, tp_base)
 OBJECT_FIELD_GETTER(PyTypeObject*, tp_bases)

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/capi/NativeCAPISymbol.java

@@ -117,6 +117,7 @@ public enum NativeCAPISymbol implements NativeCExtSymbol {
     FUN_PY_FLOAT_AS_DOUBLE("truffle_read_ob_fval"),
     FUN_GET_OB_TYPE("get_ob_type"),
     FUN_GET_OB_REFCNT("get_ob_refcnt"),
+    FUN_GET_OB_SIZE("get_ob_size"),
     FUN_GET_TP_DICT("get_tp_dict"),
     FUN_GET_TP_BASE("get_tp_base"),
     FUN_GET_TP_BASES("get_tp_bases"),