Fix an IFRT Proxy version compatibility bug introduced by ExecuteOptions::fill_status

Since `fill_status` was implicitly true before the field was introduced, we should have overridden the `fill_status` from the deserialized options. Without that, the client->server behaves incorrectly when the client is old (doesn't set `fill_status` but expects the future to be populated by the server) but the server is new (has `fill_status` in the proto and assumes that the client set it to false).

PiperOrigin-RevId: 681247988

Author: junwhanahn

third_party/xla/xla/python/ifrt_proxy/server/ifrt_backend.cc

@@ -1058,6 +1058,12 @@ IfrtBackend::HandleLoadedExecutableExecuteRequest(
   TF_ASSIGN_OR_RETURN(auto execute_options,
                       xla::ifrt::LoadedExecutable::ExecuteOptions::FromProto(
                           execute.execute_options()));
+  // Force the old behavior where `fill_status` was implicitly true before
+  // protocol version 6. Can be cleaned up once version 6 is outside the
+  // compatibility window.
+  if (version_.protocol_version() < 6) {
+    execute_options.fill_status = true;
+  }
 
   std::optional<tsl::RCReference<DeviceList>> devices;
   if (!execute.device_ids().empty()) {