[Access] Add implementation for events data providers

[Guitarheroua]

Events data providers should be implemented as part of the new WebSocket pub/sub system based on the [Draft design of new WebSockets] (#6508).

Requirements:

1. Events data provider constructors should be implemented. The constructor should create a corresponding subscription.Subscription based on input arguments, and store topic, subscription and other necessary parameters in a newly created instance. These constructors should be called in a DataProviderFactory::NewDataProvider method.

2. Run should be implemented. It will start in a forever loop until the subscription is closed. This method collects streaming data from the subscription, similar to how we do it, for example in SubscribeEventsFromStartBlockID:

flow-go/engine/access/state_stream/backend/handler.go

Lines 231 to 252 in 3496c0f

	func (h *Handler) SubscribeEventsFromStartBlockID(request *executiondata.SubscribeEventsFromStartBlockIDRequest, stream executiondata.ExecutionDataAPI_SubscribeEventsFromStartBlockIDServer) error {
	// check if the maximum number of streams is reached
	if h.StreamCount.Load() >= h.MaxStreams {
	return status.Errorf(codes.ResourceExhausted, "maximum number of streams reached")
	}
	h.StreamCount.Add(1)
	defer h.StreamCount.Add(-1)
	startBlockID, err := convert.BlockID(request.GetStartBlockId())
	if err != nil {
	return status.Errorf(codes.InvalidArgument, "could not convert start block ID: %v", err)
	}
	filter, err := h.getEventFilter(request.GetFilter())
	if err != nil {
	return err
	}
	sub := h.api.SubscribeEventsFromStartBlockID(stream.Context(), startBlockID, filter)
	return subscription.HandleSubscription(sub, h.handleEventsResponse(stream.Send, request.HeartbeatInterval, request.GetEventEncodingVersion()))
	}

Then the data is formatted in response messages for the client and written to the send callback.

Also, MessageIndex should be included in the response.

3. The Close method should be implemented to gracefully shut down the subscription.

4. ID and Topic getters should return UUID and the topic respectively.