bpo-43277: Add PySet_CheckExact to the C-API (GH-24598)

For some mysterious reason we have PySet_Check, PyFrozenSet_Check, PyAnySet_Check, PyAnySet_CheckExact and PyFrozenSet_CheckExact but no PySet_CheckExact.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 9b5898d..773eda0 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -4482,7 +4482,7 @@ _PyDictView_Intersect(PyObject* self, PyObject *other)
 
     /* if other is a set and self is smaller than other,
        reuse set intersection logic */
-    if (Py_IS_TYPE(other, &PySet_Type) && len_self <= PyObject_Size(other)) {
+    if (PySet_CheckExact(other) && len_self <= PyObject_Size(other)) {
         _Py_IDENTIFIER(intersection);
         return _PyObject_CallMethodIdObjArgs(other, &PyId_intersection, self, NULL);
     }
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 79e8451..bfe6917 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -522,7 +522,7 @@ set_repr(PySetObject *so)
         goto done;
     listrepr = tmp;
 
-    if (!Py_IS_TYPE(so, &PySet_Type))
+    if (!PySet_CheckExact(so))
         result = PyUnicode_FromFormat("%s({%U})",
                                       Py_TYPE(so)->tp_name,
                                       listrepr);