Improve ArraySegment debugging (#90488)

Author: pedrobsaila

src/libraries/System.Private.CoreLib/src/System/ArraySegment.cs

@@ -19,6 +19,8 @@ namespace System
     // (ie, users could assign a new value to the old location).
     [Serializable]
     [TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
+    [DebuggerTypeProxy(typeof(ICollectionDebugView<>))]
+    [DebuggerDisplay("Count = {Count}")]
 #pragma warning disable CA1066 // adding IEquatable<T> implementation could change semantics of code like that in xunit that queries for IEquatable vs enumerating contents
     public readonly struct ArraySegment<T> : IList<T>, IReadOnlyList<T>
 #pragma warning restore CA1066