Network cleanup (#6302)

* Cleanup network headers

* Move peerhandler to a specific header to reduce compilation times
* Move socket.cpp/h to network folder

* More work

* Network code cleanups

* Move socket.{cpp,h} to network folder
* Move Address object to network/address.{cpp,h}
* Move network exceptions to network/networkexceptions.h
* Client: use unique_ptr for Connection
* Server/ClientIface: use shared_ptr for Connection

* Format fixes

* Remove socket.cpp socket.h from clang-format whitelist

* Also fix NetworkPacket code style & make it under clang-format

src/main.cpp

@@ -39,6 +39,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "config.h"
 #include "player.h"
 #include "porting.h"
+#include "network/socket.h"
 #if USE_CURSES
 	#include "terminal_chat_console.h"
 #endif