Replace most (if not all) output << operators with to_chat(user, message)

Currently, to_chat is literally just a proc that does user << message.
But it'll let us do output modification in the future, especially for
something like Goon's HTML chat.

Big thanks to PJB for his to_chat script, see
https://github.com/d3athrow/vgstation13/pull/6625 for more details.

code/modules/computer3/computers/security.dm

@@ -58,7 +58,8 @@
 			return
 
 		if (computer.z > 6)
-			usr << "\red <b>Unable to establish a connection</b>: \black You're too far away from the station!"
+			to_chat(usr, "\red <b>Unable to establish a connection</b>: \black You're too far away from the station!")
+
 			return
 		var/dat