message: Release GIL for PyLocalBuffer::copy_to_host_async
diff: @@ -458,7 +458,8 @@ PYBIND11_MODULE(xla_extension, m) {
  py::gil_scoped_release gil_release;
  return buffer->BlockHostUntilReady();
  })
  - .def("copy_to_host_async", &PyLocalBuffer::CopyToHostAsync)
  + .def("copy_to_host_async", &PyLocalBuffer::CopyToHostAsync,
  + py::call_guard<py::gil_scoped_release>())
  .def("to_py",
  [](PyLocalBuffer* buffer) -> StatusOr<py::object> {
  GlobalPyRefManager()->CollectGarbage();
  