streaming proxy

[MarinPostma]

This PR introduces the streaming proxy RPC service. This service deprecates the old version of the proxy services, and any client using the old service should use this one instead.

The advantages of the new service are:

• The libsql connection on the primary side only lives as long as the stream is open. This solves the problem of clients disconnecting without closing connections and leaving connections open (no need for garbage collecting anymore)
• we can now stream significant request responses from primary to replica without needing to allocate the whole response
• Requests can be aborted in flight if a new request is sent to the proxy stream before the old one has finished executing, the previous one gets canceled, and the new one is processed instead.