Roundstart variation game rules (#24397)

* Raise `StationPostInitEvent` broadcast

* Basic variation pass handling

* standardize names + rule entities

* why does it work like that?

* add to defaults

* light break variation pass

* ent spawn entry

* move some stationevent utility functions to gamerule + add one for finding random tile on specified station

* forgot how statistics works

* powered light variation pass is good now

* station tile count function

* public method to ensure all solutions (for procedural use before mapinit)

* move gamerulesystem utility funcs to partial

* ensure all solutions before spilling in puddlesystem. for use when spilling before mapinit

* trash & puddle variation passes!

* oh yeah

* ehh lets live a little

* std

* utility for game rule check based on comp

* entprotoid the trash spawner oops

* generalize trash variation

* use added instead of started for secret rule

* random cleanup

* generic replacement variation system

* Wall rusting variation rule

* account for modifying while enumerating

* use localaabb

* fix test

* minor tweaks

* reinforced wall replacer + puddletweaker

Content.Server/GameTicking/Rules/VariationPass/VariationPassSystem.cs

@@ -0,0 +1,29 @@
+using Content.Server.Station.Systems;
+using Robust.Shared.Random;
+
+namespace Content.Server.GameTicking.Rules.VariationPass;
+
+/// <summary>
+///     Base class for procedural variation rule passes, which apply some kind of variation to a station,
+///     so we simply reduce the boilerplate for the event handling a bit with this.
+/// </summary>
+public abstract class VariationPassSystem<T> : GameRuleSystem<T>
+    where T: IComponent
+{
+    [Dependency] protected readonly StationSystem Stations = default!;
+    [Dependency] protected readonly IRobustRandom Random = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<T, StationVariationPassEvent>(ApplyVariation);
+    }
+
+    protected bool IsMemberOfStation(Entity<TransformComponent> ent, ref StationVariationPassEvent args)
+    {
+        return Stations.GetOwningStation(ent, ent.Comp) == args.Station.Owner;
+    }
+
+    protected abstract void ApplyVariation(Entity<T> ent, ref StationVariationPassEvent args);
+}