[mono] Use correct cast_class for IntPtr[] (#103841)

This change fixes the behavior to be like modern .NET instead of .NET Framework.

Fixes #97145

src/mono/mono/metadata/class-init.c

@@ -1039,18 +1039,14 @@ class_composite_fixup_cast_class (MonoClass *klass, gboolean for_ptr)
 	case MONO_TYPE_U2:
 		klass->cast_class = mono_defaults.int16_class;
 		break;
-	case MONO_TYPE_U4:
-#if TARGET_SIZEOF_VOID_P == 4
 	case MONO_TYPE_I:
 	case MONO_TYPE_U:
-#endif
+		klass->cast_class = mono_defaults.int_class;
+		break;
+	case MONO_TYPE_U4:
 		klass->cast_class = mono_defaults.int32_class;
 		break;
 	case MONO_TYPE_U8:
-#if TARGET_SIZEOF_VOID_P == 8
-	case MONO_TYPE_I:
-	case MONO_TYPE_U:
-#endif
 		klass->cast_class = mono_defaults.int64_class;
 		break;
 	default:

src/tests/Loader/classloader/Casting/Normalization.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.InteropServices;
+
+using Xunit;
+
+public class NormalizationTests
+{
+    [Fact]
+    public static void IntPtrArrayNormalization()
+    {
+        object x0 = new long[1];
+        object x1 = new ulong[1]; 
+
+        Assert.False(x0 is IntPtr[]);
+        Assert.False(x1 is IntPtr[]);
+    }
+}

src/tests/Loader/classloader/Casting/Normalization.csproj

@@ -0,0 +1,5 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <ItemGroup>
+    <Compile Include="Normalization.cs" />
+  </ItemGroup>
+</Project>