Comment out measure all strategy on iOS 15 for grouping (xamarin#15355)

* Update ItemsViewLayout.cs

* Update ItemsViewLayout.cs

* Make check for iOS 15.4 and higher
# Conflicts:
#	Xamarin.Forms.Platform.iOS/Forms.cs

Author: jfversluis

Xamarin.Forms.Platform.iOS/CollectionView/ItemsViewLayout.cs

@@ -170,6 +170,10 @@ public void PrepareCellForLayout(ItemsViewCell cell)
 
 		public override bool ShouldInvalidateLayout(UICollectionViewLayoutAttributes preferredAttributes, UICollectionViewLayoutAttributes originalAttributes)
 		{
+			// This is currently causing an infinite layout loop on iOS 15 https://github.com/xamarin/Xamarin.Forms/issues/15230
+			if (preferredAttributes.RepresentedElementKind == "UICollectionElementKindSectionHeader" && Forms.IsiOS154OrNewer)
+				return base.ShouldInvalidateLayout(preferredAttributes, originalAttributes);
+				
 			if (ItemSizingStrategy == ItemSizingStrategy.MeasureAllItems)
 			{
 				if (preferredAttributes.Bounds != originalAttributes.Bounds)

Xamarin.Forms.Platform.iOS/Forms.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
@@ -40,6 +40,8 @@ public static class Forms
 		static bool? s_isiOS12OrNewer;
 		static bool? s_isiOS13OrNewer;
 		static bool? s_isiOS14OrNewer;
+		static bool? s_isiOS15OrNewer;
+		static bool? s_isiOS154OrNewer;
 		static bool? s_respondsTosetNeedsUpdateOfHomeIndicatorAutoHidden;
 
 		internal static bool IsiOS9OrNewer
@@ -103,6 +105,26 @@ internal static bool IsiOS14OrNewer
 			}
 		}
 
+		internal static bool IsiOS15OrNewer
+		{
+			get
+			{
+				if (!s_isiOS15OrNewer.HasValue)
+					s_isiOS15OrNewer = UIDevice.CurrentDevice.CheckSystemVersion(15, 0);
+				return s_isiOS15OrNewer.Value;
+			}
+		}
+
+		internal static bool IsiOS154OrNewer
+		{
+			get
+			{
+				if (!s_isiOS154OrNewer.HasValue)
+					s_isiOS154OrNewer = UIDevice.CurrentDevice.CheckSystemVersion(15, 4);
+				return s_isiOS154OrNewer.Value;
+			}
+		}
+
 
 		internal static bool RespondsToSetNeedsUpdateOfHomeIndicatorAutoHidden
 		{