The NetworkManager usage was mostly for low connection counts and this
made defaults selection easy.
With more usages it is important to allow the NWM-connection to be more
configurable about memory usage and leaner in general.
This changes the headers-buffers (used to create envelopes) to not be per
connection anymore but per thread using the tread_local keyword.
This changes the ring-buffers to become configurable using
NetworkConnections::setMessageQueueSizes().
Also removing some include statements where they were not really needed
in the P2PNet lib.
This changes handling to also remove peers that fail with:
"Cannot assign requested address"
An error seen in a Docker container on a system supporting IPv6.
Additionally we now always assign a error level so an unknown error will
still cause the node to be banned after 5 attempts.
We reuse the NetworkManager lower level code in order to connect
to the Bitcoin P2P network.
This implements the basics for anyone wanting to be a player on
this network.
TomZ