Add MaxLengthAttribute support to ListControlWidget

ListControlWidget now respects the MaxLengthAttribute by disabling the add button when the collection reaches the specified maximum length. Also updated access rules to include MaxLengthAttribute.

Implements https://github.com/Facepunch/sbox-issues/issues/6361

Author: MrBrax

engine/Sandbox.Access/Rules/BaseAccess.cs

@@ -214,6 +214,7 @@ internal static partial class Rules
 		"System.ComponentModel.Annotations/System.ComponentModel.DataAnnotations.RequiredAttribute",
 		"System.ComponentModel.Annotations/System.ComponentModel.DataAnnotations.RegularExpressionAttribute",
 		"System.ComponentModel.Annotations/System.ComponentModel.DataAnnotations.RangeAttribute",
+		"System.ComponentModel.Annotations/System.ComponentModel.DataAnnotations.MaxLengthAttribute",
 
 		"System.Private.CoreLib/System.EventArgs*",
 		"System.Private.CoreLib/System.EventHandler*",

game/addons/tools/Code/Widgets/ControlWidgets/ListControlWidget.cs

@@ -1,4 +1,6 @@
-namespace Editor;
+using System.ComponentModel.DataAnnotations;
+
+namespace Editor;
 
 [CustomEditor( typeof( List<> ) )]
 [CustomEditor( typeof( Array ) )]
@@ -133,6 +135,19 @@ public void Rebuild()
 
 			if ( !ShowAddButton )
 				addButton.Visible = ShowAddButton;
+			
+			if ( SerializedProperty.TryGetAttribute<MaxLengthAttribute>( out var maxLengthAttr ) )
+			{
+				var maxLength = maxLengthAttr.Length;
+				if ( Collection is not null )
+				{
+					addButton.Enabled = Collection.Count() < maxLength;
+				}
+				else
+				{
+					addButton.Enabled = GetMultipleMin() < maxLength;
+				}
+			}
 
 			buttonRow.Add( addButton );
 			buttonRow.AddStretchCell( 1 );