Revert biome rework (#38724)

* Revert "Fix world generation (#38713)"

This reverts commit 10fa6ff4af.

* Revert "Biome rework (#37735)"

This reverts commit fe7b96147c.

Content.Shared/Parallax/Biomes/Layers/BiomeDummyLayer.cs

@@ -0,0 +1,18 @@
+using Robust.Shared.Noise;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Parallax.Biomes.Layers;
+
+/// <summary>
+/// Dummy layer that specifies a marker to be replaced by external code.
+/// For example if they wish to add their own layers at specific points across different templates.
+/// </summary>
+[Serializable, NetSerializable]
+public sealed partial class BiomeDummyLayer : IBiomeLayer
+{
+    [DataField("id", required: true)] public string ID = string.Empty;
+
+    public FastNoiseLite Noise { get; } = new();
+    public float Threshold { get; }
+    public bool Invert { get; }
+}