bug: delay when using lightpush

[chaitanyaprem]

Problem

Observed the below while dogfooding status-desktop using lightpush.

If a single message is sent , message is delivered almost instantly
When multiple messages are sent in succession, then a significant delay in message delivery is observed which keeps increasing with each mesage sent.

Implementation

On debugging further noticed that in status-go, a single queue which sends a message via lightpush and waits for response from lightpush node before next message is sent. This is causing the significant delay in delivery.
ref code:

status-go/wakuv2/waku.go

Lines 1028 to 1037 in b52a9ce

	case envelope := <-w.sendQueue:
	pubsubTopic := envelope.PubsubTopic()
	var err error
	logger := w.logger.With(zap.String("envelopeHash", hexutil.Encode(envelope.Hash())), zap.String("pubsubTopic", pubsubTopic), zap.String("contentTopic", envelope.Message().ContentTopic), zap.Int64("timestamp", envelope.Message().GetTimestamp()))
	// For now only used in testing to simulate going offline
	if w.settings.SkipPublishToTopic {
	err = errors.New("Test send failure")
	} else if w.settings.LightClient {
	w.logger.Info("publishing message via lightpush")
	_, err = w.node.Lightpush().Publish(w.ctx, envelope.Message(), lightpush.WithPubSubTopic(pubsubTopic))

.

This needs to be done asynchronously in order to avoid the delay observed while using lightpush.

Quoting @richard-ramos I guess that code could be put into a goroutine. The important part is to call w.SendEnvelopeEvent(event) after the message is sent indicating if it was sent succesfully or not

Acceptance Criteria

When using lightMode, sending messages in succession should not have delay in delivering the same.

Future Steps

Ensure all lightpush related tests pass.
Need to ensure to test cases where there is a lot of network connectivity, messages to be sent are either sent successfully or marked for resend.

[chair28980]

Addressed in #4466 (develop branch) and #4467 (test-shard-test release branch).