Extend query functionality to support streams

[skreborn]

Currently, Zenoh only supports a simple query mechanism where the client sends a single message and the server (or multiple servers) sends back one or more responses before closing the query.

However, all the responses from a single server are delivered to the client at the same time - they are buffered and sent as one instead of being continuously streamed. This means that query handlers both can't receive or reply with a stream of messages.

A good model that supports all combinations of single and streaming inputs and outputs is gRPC. It practically has everything I wish Zenoh provided with the query functionality.

Of course, the reason I use Zenoh is for its distributed fashion and versatility, and I understand that this model comes with its own challanges. Something to decide is what happens if multiple query handlers reply to the same request, and I hope that implementing multiple response streams is a possibility.