Adds support for a map rotation system. (#7162)

* Adds support for a map rotation system.
It is now the default way of selecting a map, map votes have been disabled.

* whoops

* Randomize the map it starts off with, too.
(it'd pick bagel every time otherwise)

* Address review

* remove knight from rotation due to it being an unmaintained map.

* minor cleanup

Content.Shared/CCVar/CCVars.cs

@@ -126,6 +126,19 @@ namespace Content.Shared.CCVar
         public static readonly CVarDef<bool>
             GameMapForced = CVarDef.Create("game.mapforced", false, CVar.SERVERONLY);
 
+        /// <summary>
+        /// The depth of the queue used to calculate which map is next in rotation.
+        /// This is how long the game "remembers" that some map was put in play. Default is 16 rounds.
+        /// </summary>
+        public static readonly CVarDef<int>
+            GameMapMemoryDepth = CVarDef.Create("game.map_memory_depth", 16, CVar.SERVERONLY);
+
+        /// <summary>
+        /// Is map rotation enabled?
+        /// </summary>
+        public static readonly CVarDef<bool>
+            GameMapRotation = CVarDef.Create<bool>("game.map_rotation", true, CVar.SERVERONLY);
+
         /// <summary>
         ///     Whether a random position offset will be applied to the station on roundstart.
         /// </summary>
@@ -562,7 +575,7 @@ namespace Content.Shared.CCVar
         ///     See vote.enabled, but specific to map votes
         /// </summary>
         public static readonly CVarDef<bool> VoteMapEnabled =
-            CVarDef.Create("vote.map_enabled", true, CVar.SERVERONLY);
+            CVarDef.Create("vote.map_enabled", false, CVar.SERVERONLY);
 
         /// <summary>
         ///     The required ratio of the server that must agree for a restart round vote to go through.