Issue #9630: Redecode filenames when setting the filesystem encoding

Redecode the filenames of:

 - all modules: __file__ and __path__ attributes
 - all code objects: co_filename attribute
 - sys.path
 - sys.meta_path
 - sys.executable
 - sys.path_importer_cache (keys)

Keep weak references to all code objects until initfsencoding() is called, to
be able to redecode co_filename attribute of all code objects.

Objects/codeobject.c

@@ -5,6 +5,8 @@
 #define NAME_CHARS \
     "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz"
 
+PyObject *_Py_code_object_list = NULL;
+
 /* all_name_chars(s): true iff all chars in s are valid NAME_CHARS */
 
 static int
@@ -109,8 +111,23 @@ PyCode_New(int argcount, int kwonlyargcount,
         co->co_lnotab = lnotab;
         co->co_zombieframe = NULL;
         co->co_weakreflist = NULL;
+
+        if (_Py_code_object_list != NULL) {
+            int err;
+            PyObject *ref = PyWeakref_NewRef((PyObject*)co, NULL);
+            if (ref == NULL)
+                goto error;
+            err = PyList_Append(_Py_code_object_list, ref);
+            Py_DECREF(ref);
+            if (err)
+                goto error;
+        }
     }
     return co;
+
+error:
+    Py_DECREF(co);
+    return NULL;
 }
 
 PyCodeObject *