bpo-35568: add 'raise_signal' function (GH-11335)

As in title, expose C `raise` function as `raise_function` in `signal` module. Also drop existing `raise_signal` in `_testcapi` module and replace all usages with new function.


https://bugs.python.org/issue35568

Modules/_testcapimodule.c

@@ -3859,25 +3859,6 @@ exit:
     return res;
 }
 
-static PyObject*
-test_raise_signal(PyObject* self, PyObject *args)
-{
-    int signum, err;
-
-    if (!PyArg_ParseTuple(args, "i:raise_signal", &signum)) {
-        return NULL;
-    }
-
-    err = raise(signum);
-    if (err)
-        return PyErr_SetFromErrno(PyExc_OSError);
-
-    if (PyErr_CheckSignals() < 0)
-        return NULL;
-
-    Py_RETURN_NONE;
-}
-
 /* marshal */
 
 static PyObject*
@@ -4908,8 +4889,6 @@ static PyMethodDef TestMethods[] = {
     {"docstring_with_signature_with_defaults",
         (PyCFunction)test_with_docstring, METH_NOARGS,
         docstring_with_signature_with_defaults},
-    {"raise_signal",
-     (PyCFunction)test_raise_signal, METH_VARARGS},
     {"call_in_temporary_c_thread", call_in_temporary_c_thread, METH_O,
      PyDoc_STR("set_error_class(error_class) -> None")},
     {"pymarshal_write_long_to_file",