Add GRContext Metal backend test

Author: jeremy-visionaid

tests/SkiaSharp.Tests.Devices/Tests/iOS/iOSExtensionsTests.cs

@@ -1,5 +1,7 @@
-using CoreGraphics;
+using System;
+using CoreGraphics;
 using Foundation;
+using Metal;
 using Xunit;
 
 namespace SkiaSharp.Views.iOS.Tests
@@ -99,5 +101,28 @@ public void CGRectToSKRect(int x, int y, int w, int h)
 
 			Assert.Equal(expected, actual);
 		}
+
+		[Fact]
+		public void GRContextDoesNotCrash()
+		{
+			CreateAndDisposeMetalGRContext();
+			CreateAndDisposeMetalGRContext();
+		}
+
+		private static void CreateAndDisposeMetalGRContext()
+		{
+			var device = MTLDevice.SystemDefault!;
+			using (var backendContext = new GRMtlBackendContext()
+			{
+				Device = device,
+				Queue = device.CreateCommandQueue(),
+			})
+			{
+				using var context = GRContext.CreateMetal(backendContext);
+			}
+
+			GC.Collect();
+			GC.WaitForPendingFinalizers();
+		}
 	}
 }