message: [XLA:Python] Add AllGather to HLO bindings.
  First step in fixing
diff: @@ -50,6 +50,11 @@ void BuildOpsSubmodule(py::module* m) {
  .value("ADJOINT", TriangularSolveOptions::ADJOINT);
  ops.def("AfterAll", &AfterAll, py::arg("builder"), py::arg("tokens"));
  + ops.def("AllGather", &AllGather, py::arg("operand"),
  + py::arg("all_gather_dimension"), py::arg("shard_count"),
  + py::arg("replica_groups") = py::list(),
  + py::arg("channel_id") = absl::nullopt,
  + py::arg("shape_with_layout") = absl::nullopt);
  ops.def(
  "AllReduce",
  static_cast<XlaOp (*)(
  