Fix remaining uses of ._PyType member in extension code

This should be replaced with Dtool_GetPyTypeObject, hiding the implementation details a bit so that we can more easily change the underlying structure if we need later

Also adds Py_NewRef to py_compat.h, backporting from master

dtool/src/interrogatedb/py_compat.h

@@ -247,6 +247,28 @@ INLINE PyObject *PyObject_CallMethodOneArg(PyObject *obj, PyObject *name, PyObje
 }
 #endif
 
+/* Python 3.10 */
+
+#if PY_VERSION_HEX < 0x030A0000
+INLINE int PyModule_AddObjectRef(PyObject *module, const char *name, PyObject *value) {
+  int ret = PyModule_AddObject(module, name, value);
+  if (ret == 0) {
+    Py_INCREF(value);
+  }
+  return ret;
+}
+
+ALWAYS_INLINE PyObject *Py_NewRef(PyObject *obj) {
+  Py_INCREF(obj);
+  return obj;
+}
+
+ALWAYS_INLINE PyObject *Py_XNewRef(PyObject *obj) {
+  Py_XINCREF(obj);
+  return obj;
+}
+#endif
+
 /* Python 3.12 */
 
 #if PY_VERSION_HEX < 0x030C0000

panda/src/express/datagram_ext.I

@@ -52,10 +52,10 @@ __reduce__() const {
   }
 
   extern struct Dtool_PyTypedObject Dtool_Datagram;
-  Py_INCREF((PyObject *)&Dtool_Datagram._PyType);
+  PyObject *tp = (PyObject *)Dtool_GetPyTypeObject(&Dtool_Datagram);
 
   PyObject *result = PyTuple_New(2);
-  PyTuple_SET_ITEM(result, 0, (PyObject *)&Dtool_Datagram._PyType);
+  PyTuple_SET_ITEM(result, 0, Py_NewRef(tp));
   PyTuple_SET_ITEM(result, 1, args);
   return result;
 }

panda/src/express/pointerToArray_ext.I

@@ -100,7 +100,7 @@ __init__(PyObject *self, PyObject *source) {
 
   // Now construct the internal list by copying the elements one-at-a-time
   // from Python.
-  PyObject *dict = DtoolInstance_TYPE(self)->_PyType.tp_dict;
+  PyObject *dict = Dtool_GetPyTypeObject(DtoolInstance_TYPE(self))->tp_dict;
   PyObject *push_back = PyDict_GetItemString(dict, "push_back");
   if (push_back == nullptr) {
     PyErr_BadArgument();