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/EntitySpawnVariationPassSystem.cs

@@ -0,0 +1,29 @@
+using Content.Server.GameTicking.Rules.VariationPass.Components;
+using Content.Shared.Storage;
+using Robust.Shared.Random;
+
+namespace Content.Server.GameTicking.Rules.VariationPass;
+
+/// <inheritdoc cref="EntitySpawnVariationPassComponent"/>
+public sealed class EntitySpawnVariationPassSystem : VariationPassSystem<EntitySpawnVariationPassComponent>
+{
+    protected override void ApplyVariation(Entity<EntitySpawnVariationPassComponent> ent, ref StationVariationPassEvent args)
+    {
+        var totalTiles = Stations.GetTileCount(args.Station);
+
+        var dirtyMod = Random.NextGaussian(ent.Comp.TilesPerEntityAverage, ent.Comp.TilesPerEntityStdDev);
+        var trashTiles = Math.Max((int) (totalTiles * (1 / dirtyMod)), 0);
+
+        for (var i = 0; i < trashTiles; i++)
+        {
+            if (!TryFindRandomTileOnStation(args.Station, out _, out _, out var coords))
+                continue;
+
+            var ents = EntitySpawnCollection.GetSpawns(ent.Comp.Entities, Random);
+            foreach (var spawn in ents)
+            {
+                SpawnAtPosition(spawn, coords);
+            }
+        }
+    }
+}