Application side nukleus should be able to set/negotiate protocol

[Related spec test](https://github.com/reaktivity/nukleus-ws.spec/blob/754f7b9cd033606499c575eddc7b0b88fc727735/src/main/scripts/org/reaktivity/specification/ws/opening/response.header.sec.websocket.protocol.not.negotiated/handshake.request.rpt)