logs: replace every fmt::print with a lg call instead (#1368)

Favors the `lg` namespace over `fmt` directly, as this will output the
logs to a file / has log levels.

I also made assertion errors go to a file, this unfortunately means
importing `lg` and hence `fmt` which was attempted to be avoided before.
But I'm not sure how else to do this aspect without re-inventing the
file logging.

We have a lot of commented out prints as well that we should probably
cleanup at some point / switch them to trace level and default to `info`
level.

I noticed the pattern of disabling debug logs behind some boolean,
something to consider cleaning up in the future -- if our logs were more
structured (knowing where they are coming from) then a lot this
boilerplate could be eliminated.

Closes #1358

game/system/Deci2Server.cpp

@@ -21,6 +21,7 @@
 #include <WinSock2.h>
 #include <WS2tcpip.h>
 #endif
+#include "common/log/log.h"
 // clang-format on
 
 Deci2Server::~Deci2Server() {
@@ -37,7 +38,7 @@ Deci2Server::~Deci2Server() {
 }
 
 void Deci2Server::post_init() {
-  fmt::print("[Deci2Server:{}] awaiting connections\n", tcp_port);
+  lg::info("[Deci2Server:{}] awaiting connections", tcp_port);
   accept_thread_running = true;
   kill_accept_thread = false;
   accept_thread = std::thread(&Deci2Server::accept_thread_func, this);