Add internal _UseManagedNtlm feature switch (#34903)

Author: wfurt

src/Assets/TestProjects/KitchenSink/TestApp/TestApp.csproj

@@ -42,6 +42,7 @@
     <ThreadPoolMinThreads>2</ThreadPoolMinThreads>
     <ThreadPoolMaxThreads>9</ThreadPoolMaxThreads>
     <UseWindowsThreadPool>true</UseWindowsThreadPool>
+    <_UseManagedNtlm>true</_UseManagedNtlm>
   </PropertyGroup>
 
   <ItemGroup>

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets

@@ -550,6 +550,11 @@ Copyright (c) .NET Foundation. All rights reserved.
                                     Value="$(UseNativeHttpHandler)"
                                     Trim="true" />
 
+    <RuntimeHostConfigurationOption Include="System.Net.Security.UseManagedNtlm"
+                                    Condition="'$(_UseManagedNtlm)' != ''"
+                                    Value="$(_UseManagedNtlm)"
+                                    Trim="true" />
+
     <RuntimeHostConfigurationOption Include="System.Reflection.Metadata.MetadataUpdater.IsSupported"
                                     Condition="'$(MetadataUpdaterSupport)' != ''"
                                     Value="$(MetadataUpdaterSupport)"

src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishAProjectWithAllFeatures.cs

@@ -68,6 +68,7 @@ public void It_publishes_the_project_correctly(string targetFramework, string[]
             ""System.GC.RetainVM"": false,
             ""System.Net.Http.EnableActivityPropagation"": false,
             ""System.Net.Http.UseNativeHttpHandler"": true,
+            ""System.Net.Security.UseManagedNtlm"": true,
             ""System.Reflection.Metadata.MetadataUpdater.IsSupported"": false,
             ""System.Reflection.NullabilityInfoContext.IsSupported"": false,
             ""System.Resources.ResourceManager.AllowCustomResourceTypes"": false,