bpo-34042: Fix dict.copy() to maintain correct total refcount (GH-8119)

(cherry picked from commit 0b75228700e0077d8bf2636e74733389514b4b2f)

Co-authored-by: Yury Selivanov <yury@magic.io>
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 7a1bceb..828eb99 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -656,6 +656,13 @@
         /* Maintain tracking. */
         _PyObject_GC_TRACK(new);
     }
+
+    /* Since we copied the keys table we now have an extra reference
+       in the system.  Manually call _Py_INC_REFTOTAL to signal that
+       we have it now; calling DK_INCREF would be an error as
+       keys->dk_refcnt is already set to 1 (after memcpy). */
+    _Py_INC_REFTOTAL;
+
     return (PyObject *)new;
 }