Leverage the TGS4 chat tagging system for the new game message (#41697)

Allows specifying the tag to send the game announce message to on TGS4

Needed by downstreams

code/controllers/configuration/entries/general.dm

@@ -390,6 +390,13 @@
 	integer = FALSE
 
 /datum/config_entry/flag/irc_announce_new_game
+	deprecated_by = /datum/config_entry/string/chat_announce_new_game
+
+/datum/config_entry/flag/irc_announce_new_game/DeprecationUpdate(value)
+	return ""	//default broadcast
+
+/datum/config_entry/string/chat_announce_new_game
+	config_entry_value = null
 
 /datum/config_entry/flag/debug_admin_hrefs
 

code/controllers/subsystem/ticker.dm

@@ -136,8 +136,7 @@ SUBSYSTEM_DEF(ticker)
 			for(var/client/C in GLOB.clients)
 				window_flash(C, ignorepref = TRUE) //let them know lobby has opened up.
 			to_chat(world, "<span class='boldnotice'>Welcome to [station_name()]!</span>")
-			if(CONFIG_GET(flag/irc_announce_new_game))
-				world.TgsTargetedChatBroadcast("New round starting on [SSmapping.config.map_name]!", FALSE)
+			send2chat("New round starting on [SSmapping.config.map_name]!", CONFIG_GET(string/chat_announce_new_game))
 			current_state = GAME_STATE_PREGAME
 			//Everyone who wants to be an observer is now spawned
 			create_observers()