DungeonData rework (#37172)

* DungeonData rework

Back to fields, serializes better, just make new layers dumby.

* wawawewa

* Fix this

* Fixes

* review

* thanks fork

* fix

Content.Shared/Procedural/PostGeneration/CornerClutterDunGen.cs

@@ -1,14 +1,17 @@
+using Content.Shared.EntityTable;
+using Content.Shared.Storage;
+using Robust.Shared.Prototypes;
+
 namespace Content.Shared.Procedural.PostGeneration;
 
 /// <summary>
 /// Spawns entities inside corners.
 /// </summary>
-/// <remarks>
-/// Dungeon data keys are:
-/// - CornerClutter
-/// </remarks>
 public sealed partial class CornerClutterDunGen : IDunGenLayer
 {
     [DataField]
     public float Chance = 0.50f;
+
+    [DataField(required:true)]
+    public ProtoId<EntityTablePrototype> Contents = new();
 }