extend micro, broker, server, client interfaces

[vtolstov]

micro: https://pkg.go.dev/github.com/unistack-org/micro/v3#RegisterSubscriber

• RegisterSubscriber func signature to support multiple messages

broker: https://pkg.go.dev/github.com/unistack-org/micro/v3/broker?utm_source=godoc#Broker * allow to publish multiple messages at once (batch producing) * allow to subscribe and handle multiple messages at once (batch consuming)

server:

• allow to support handler type that supports multiple messages

  client:

• allow to publish multiple messages