Bugfix: System.Xml.Serialization: Compiler.GetTempAssemblyName is not deterministic under .NET Core (#46499)

* Bugfix: System.Xml.Serialization: Compiler.GetTempAssemblyName is not persistent under .NET Core

The implementation of String.GetHashCode() was persistent by default in .NET Framework. allowing to predictably name an XmlSerializers.{HashCode}.dll containing the pre-generated serializers.
In .NET Core / .NET 5, String.GetHashCode() is no longer persistent, so the value of ns.GetHashCode() will change during each run, preventing it from picking up the XmlSerializers dll correctly.

* Remove trailing whitespace

* Use truncated SHA512

* Fixed compilation

* Dispose SHA512 instance

* Fixed compilation

* Update src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compiler.cs

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Update src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compiler.cs

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Update Compiler.cs

Co-authored-by: Stephen Toub <stoub@microsoft.com>

Author: TalAloni

src/libraries/System.Private.Xml/src/System.Private.Xml.csproj

@@ -567,6 +567,7 @@
     <Reference Include="System.Runtime.Extensions" />
     <Reference Include="System.Runtime.InteropServices" />
     <Reference Include="System.Security.Cryptography.Algorithms" />
+    <Reference Include="System.Security.Cryptography.Primitives" />
     <Reference Include="System.Text.Encoding.Extensions" />
     <Reference Include="System.Text.RegularExpressions" />
     <Reference Include="System.Threading" />

src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compiler.cs

@@ -1,13 +1,16 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Reflection;
+using System.Buffers.Binary;
 using System.Collections;
-using System.IO;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
+using System.IO;
+using System.Reflection;
 using System.Runtime.CompilerServices;
-using System.Diagnostics.CodeAnalysis;
+using System.Security.Cryptography;
+using System.Text;
 
 namespace System.Xml.Serialization
 {
@@ -89,7 +92,14 @@ internal TextWriter Source
 
         internal static string GetTempAssemblyName(AssemblyName parent, string? ns)
         {
-            return parent.Name + ".XmlSerializers" + (ns == null || ns.Length == 0 ? "" : "." + ns.GetHashCode());
+            return parent.Name + ".XmlSerializers" + (string.IsNullOrEmpty(ns) ? "" : $".{GetPersistentHashCode(ns)}");
+        }
+
+        private static uint GetPersistentHashCode(string value)
+        {
+            byte[] valueBytes = Encoding.UTF8.GetBytes(value);
+            byte[] hash = SHA512.HashData(valueBytes);
+            return BinaryPrimitives.ReadUInt32BigEndian(hash);
         }
     }
 }