bpo-41078: Fix bltinmodule.c with Py_TRACE_REFS (GH-21058)

Add pycore_object.h include to fix bltinmodule.c when Py_TRACE_REFS
macro is defined.

Author: vstinner

Python/bltinmodule.c

@@ -4,6 +4,7 @@
 #include <ctype.h>
 #include "ast.h"
 #undef Yield   /* undefine macro conflicting with <winbase.h> */
+#include "pycore_object.h"        // _Py_AddToAllObjects()
 #include "pycore_pyerrors.h"      // _PyErr_NoMemory()
 #include "pycore_pystate.h"       // _PyThreadState_GET()
 #include "pycore_tuple.h"         // _PyTuple_FromArray()