No atmos stacking (attempt 2) (#16687)

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/Construction/Conditions/NoUnstackableInTile.cs

@@ -0,0 +1,31 @@
+using Content.Shared.Construction.EntitySystems;
+using JetBrains.Annotations;
+using Robust.Shared.Map;
+
+namespace Content.Shared.Construction.Conditions;
+
+/// <summary>
+///   Check for "Unstackable" condition commonly used by atmos devices and others which otherwise don't check on
+///   collisions with other items.
+/// </summary>
+[UsedImplicitly]
+[DataDefinition]
+public sealed class NoUnstackableInTile : IConstructionCondition
+{
+    public const string GuidebookString = "construction-step-condition-no-unstackable-in-tile";
+    public bool Condition(EntityUid user, EntityCoordinates location, Direction direction)
+    {
+        var sysMan = IoCManager.Resolve<IEntitySystemManager>();
+        var anchorable = sysMan.GetEntitySystem<SharedAnchorableSystem>();
+
+        return !anchorable.AnyUnstackablesAnchoredAt(location);
+    }
+
+    public ConstructionGuideEntry GenerateGuideEntry()
+    {
+        return new ConstructionGuideEntry
+        {
+            Localization = GuidebookString
+        };
+    }
+}