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/upload/programs.dm

@@ -8,6 +8,7 @@
 		if(!interactable() || istype(usr,/mob/living/silicon))
 			return 0
 		if(!computer.net)
-			usr << "An indecipherable set of code flicks across the screen.  Nothing else happens."
+			to_chat(usr, "An indecipherable set of code flicks across the screen.  Nothing else happens.")
+
 			return
 		var/list/results = computer.net.get_machines