Immovable Rod visual variations (#25932)

* Adds variations to immovable rod

* slash oopsie

* Changed prototypes from being hardcoded to being defined in the rules component

* Changed from 10% chance to 5%

* Changes based on feedback

* Fix nullable error

* Moved randomized logic to .yaml. Probabilities of alternate rods add up to 5%.

Content.Server/StationEvents/Components/ImmovableRodRuleComponent.cs

@@ -1,4 +1,5 @@
 using Content.Server.StationEvents.Events;
+using Content.Shared.Storage;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototype;
 
@@ -7,6 +8,8 @@ namespace Content.Server.StationEvents.Components;
 [RegisterComponent, Access(typeof(ImmovableRodRule))]
 public sealed partial class ImmovableRodRuleComponent : Component
 {
-    [DataField("rodPrototype", customTypeSerializer: typeof(PrototypeIdSerializer<EntityPrototype>))]
-    public string RodPrototype = "ImmovableRodKeepTilesStill";
+    ///     List of possible rods and spawn probabilities.
+    /// </summary>
+    [DataField]
+    public List<EntitySpawnEntry> RodPrototypes = new();
 }