bpo-40268: Add _PyInterpreterState_GetConfig() (GH-19492)

Don't access PyInterpreterState.config member directly anymore, but
use new functions:

* _PyInterpreterState_GetConfig()
* _PyInterpreterState_SetConfig()
* _Py_GetConfig()
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 7be075b..30bc739 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -7,7 +7,6 @@
 #include "pycore_bytes_methods.h"
 #include "pycore_object.h"
 #include "pycore_pymem.h"
-#include "pycore_pystate.h"
 
 #include "pystrhex.h"
 #include <stddef.h>
@@ -1342,8 +1341,7 @@
 static PyObject *
 bytes_str(PyObject *op)
 {
-    PyConfig *config = &_PyInterpreterState_GET_UNSAFE()->config;
-    if (config->bytes_warning) {
+    if (_Py_GetConfig()->bytes_warning) {
         if (PyErr_WarnEx(PyExc_BytesWarning,
                          "str() on a bytes instance", 1)) {
             return NULL;
@@ -1500,8 +1498,7 @@
 
     /* Make sure both arguments are strings. */
     if (!(PyBytes_Check(a) && PyBytes_Check(b))) {
-        PyConfig *config = &_PyInterpreterState_GET_UNSAFE()->config;
-        if (config->bytes_warning && (op == Py_EQ || op == Py_NE)) {
+        if (_Py_GetConfig()->bytes_warning && (op == Py_EQ || op == Py_NE)) {
             rc = PyObject_IsInstance((PyObject*)a,
                                      (PyObject*)&PyUnicode_Type);
             if (!rc)