Add radiators (#18728)

* Add radiators

* Limit heat transfer to fluid heat capacity

* Adjust datafield names

* Fix material arbitrage

* This code has been debugged, and so there are no more bugs. Debugging code is therefore unnecessary

* Adjust radiator layer subfloor visibility

* Cache CVars

* No default

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

* Like and unsubscribe

* Fix CVar caching

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Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

Content.Shared/CCVar/CCVars.cs

@@ -937,6 +937,12 @@ namespace Content.Shared.CCVar
         public static readonly CVarDef<bool> Superconduction =
             CVarDef.Create("atmos.superconduction", false, CVar.SERVERONLY);
 
+        /// <summary>
+        ///     Heat loss per tile due to radiation at 20 degC, in W.
+        /// </summary>
+        public static readonly CVarDef<float> SuperconductionTileLoss =
+            CVarDef.Create("atmos.superconduction_tile_loss", 30f, CVar.SERVERONLY);
+
         /// <summary>
         ///     Whether excited groups will be processed and created.
         /// </summary>