gdb: Introduce 'scylla netw' command
gdb: Introduce 'scylla netw' command

Prints information about the state of the messaging service layer.

Example:

(gdb) scylla netw
Dropped messages: {0 <repeats 25 times>}
Outgoing connections:
IP: 127.0.0.2, (netw::messaging_service::rpc_protocol_client_wrapper*) 0x6000051cd220:
  stats: {replied = 0, pending = 0, exception_received = 0, sent_messages = 23, wait_reply = 0, timeout = 0}
  outstanding: 0
Server: resources={_count = 85899345, _ex = {_M_exception_object = 0x0}, _wait_list = {_list = {_front_chunk = 0x0, _back_chunk = 0x0, _nchunks = 0, _free_chunks = 0x0, _nfree_chunks = 0}, _on_expiry = {<No data fields>}, _size = 0}}
Incoming connections:
127.0.0.1:28071:
   {replied = 0, pending = 0, exception_received = 0, sent_messages = 2, wait_reply = 0, timeout = 0}

avikivity/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla