Cleanup mimic event (#23705)

* Cleanup mimic event

Now it won't be forced on dev map or mapping mode.

* Minor cleanup

Content.Server/Antag/Mimic/MobReplacementRuleComponent.cs

@@ -0,0 +1,21 @@
+using Robust.Shared.Prototypes;
+
+namespace Content.Server.Antag.Mimic;
+
+/// <summary>
+/// Replaces the relevant entities with mobs when the game rule is started.
+/// </summary>
+[RegisterComponent]
+public sealed partial class MobReplacementRuleComponent : Component
+{
+    // If you want more components use generics, using a whitelist would probably kill the server iterating every single entity.
+
+    [DataField]
+    public EntProtoId Proto = "MobMimic";
+
+    /// <summary>
+    /// Chance per-entity.
+    /// </summary>
+    [DataField]
+    public float Chance = 0.001f;
+}

Content.Server/Antag/MobReplacementRuleSystem.cs

@@ -0,0 +1,37 @@
+using Content.Server.Antag.Mimic;
+using Content.Server.GameTicking.Rules;
+using Content.Server.GameTicking.Rules.Components;
+using Content.Shared.VendingMachines;
+using Robust.Shared.Map;
+using Robust.Shared.Random;
+
+namespace Content.Server.Antag;
+
+public sealed class MobReplacementRuleSystem : GameRuleSystem<MobReplacementRuleComponent>
+{
+    [Dependency] private readonly IRobustRandom _random = default!;
+
+    protected override void Started(EntityUid uid, MobReplacementRuleComponent component, GameRuleComponent gameRule, GameRuleStartedEvent args)
+    {
+        base.Started(uid, component, gameRule, args);
+
+        var query = AllEntityQuery<VendingMachineComponent, TransformComponent>();
+        var spawns = new List<(EntityUid Entity, EntityCoordinates Coordinates)>();
+
+        while (query.MoveNext(out var vendingUid, out _, out var xform))
+        {
+            if (!_random.Prob(component.Chance))
+                continue;
+
+            spawns.Add((vendingUid, xform.Coordinates));
+        }
+
+        foreach (var entity in spawns)
+        {
+            var coordinates = entity.Coordinates;
+            Del(entity.Entity);
+
+            Spawn(component.Proto, coordinates);
+        }
+    }
+}