Remove SpreaderNodeGroup (#20230)

* Remove SpreaderNodeGroup

* Fix airtight updates

* more smoke stuff

* more smoke fixes

* wtf is smoke code

* Fix merge

* Fix divide by zero

Content.Server/Spreader/ActiveEdgeSpreaderComponent.cs

@@ -0,0 +1,10 @@
+namespace Content.Server.Spreader;
+
+/// <summary>
+/// Added to entities being considered for spreading via <see cref="SpreaderSystem"/>.
+/// This needs to be manually added and removed.
+/// </summary>
+[RegisterComponent]
+public sealed partial class ActiveEdgeSpreaderComponent : Component
+{
+}