Salvage dungeons (#14520)

Content.Shared/Procedural/Dungeon.cs

@@ -0,0 +1,11 @@
+namespace Content.Shared.Procedural;
+
+public sealed class Dungeon
+{
+    public List<DungeonRoom> Rooms = new();
+
+    /// <summary>
+    /// Hashset of the tiles across all rooms.
+    /// </summary>
+    public HashSet<Vector2i> RoomTiles = new();
+}