Implement optimal lazy initialization strategy for RoutingSender

[nieznanysprawiciel]

Why:

• Calling RoutingSender::send will try to re-initialize session, if it was closed. This is good idea in certain scenarios, but everything depends on the reason that session was closed.

Examples:

• Other Node shutdown - re-initialization will fail anyway
• Temporarily internet connection was lost - in this case we would like to continue sending packets after connection will start working again
• Initialization with Node failed, because it was sending incorrect protocol messages - it's not clear if we want to talk with this Node (it can be either malicious or it works incorrectly)

What:

• Consider what are possible cases of re-initialization scenarios
• Plan the best strategy possible
• Implement RoutingSender
• Check if TcpSender has any similarities in terms of optimal strategy

[staszek-krotki]

Looks like an optimization without significant value added