Return emitted data in case of emission error.

[Totodore]

Fix #172

There are two remaining questions :

• What should be done with binary packets. Because a message can contain N binary payloads it means that we would need N+1 Permits for each emit call.
• What should be done when broadcasting. What is the performance cost of asking X Permits from N sockets at the same time ? Because packet is encoded only once and then cloned many times to be sent. Maybe it would be better to just clone the data before sending anything so it is possible to send it back to the user.
  Also broadcasting is done through Operators, and Operators are not always used to broadcast, they can be used to simply add a timeout or a binary payload when emitting. So the emit signature needs to be the same from the Operator fn even if it is not broadcasting.

• The new reserve_many API on tokio v1.36 resolves the first question.
• The second problem still needs to be resolved.

[Totodore]

What should be done when broadcasting. What is the performance cost of asking X Permits from N sockets at the same time ? Because packet is encoded only once and then cloned many times to be sent. Maybe it would be better to just clone the data before sending anything so it is possible to send it back to the user.
Also broadcasting is done through Operators, and Operators are not always used to broadcast, they can be used to simply add a timeout or a binary payload when emitting. So the emit signature needs to be the same from the Operator fn even if it is not broadcasting.

Because operators are now splitted between ConfOperators and BroadcastOperators it is possible to separate the code between broadcasting and single emission with configuration (binary, timeout, etc). There are two main advantages:

• Single emission with configuration is more performant because it is directly done on the socket. Before the adapter was called to fetch the concerned socket.
• It is possible to return the emitted data in case of emission error for:
  • emit
  • emit_with_ack

[Totodore]

Maybe it would be worth it to think about a better pattern, in order to avoid code duplication between ConfOperators and BroadcastOperators...