[Blazor] Make multithreading APIs internal (#57286)

Author: javiercn

src/Components/WebAssembly/Server/src/Builder/WebAssemblyComponentsEndpointOptions.cs

@@ -25,7 +25,7 @@ public sealed class WebAssemblyComponentsEndpointOptions
     /// Note that enabling this feature can restrict your ability to use other JavaScript APIs. For more
     /// information, see <see href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer#security_requirements" />.
     /// </summary>
-    public bool ServeMultithreadingHeaders { get; set; }
+    internal bool ServeMultithreadingHeaders { get; set; }
 
     /// <summary>
     /// Gets or sets the <see cref="string"/> that determines the static assets manifest path mapped to this app.

src/Components/WebAssembly/Server/src/Microsoft.AspNetCore.Components.WebAssembly.Server.csproj

@@ -20,6 +20,7 @@
 
   <ItemGroup>
     <InternalsVisibleTo Include="Microsoft.AspNetCore.Components.WebAssembly.Server.Tests" />
+    <InternalsVisibleTo Include="ThreadingApp.Server" />
   </ItemGroup>
 
   <ItemGroup>

src/Components/WebAssembly/Server/src/PublicAPI.Unshipped.txt

@@ -5,8 +5,6 @@ Microsoft.AspNetCore.Components.WebAssembly.Server.AuthenticationStateSerializat
 Microsoft.AspNetCore.Components.WebAssembly.Server.AuthenticationStateSerializationOptions.SerializationCallback.set -> void
 Microsoft.AspNetCore.Components.WebAssembly.Server.AuthenticationStateSerializationOptions.SerializeAllClaims.get -> bool
 Microsoft.AspNetCore.Components.WebAssembly.Server.AuthenticationStateSerializationOptions.SerializeAllClaims.set -> void
-Microsoft.AspNetCore.Components.WebAssembly.Server.WebAssemblyComponentsEndpointOptions.ServeMultithreadingHeaders.get -> bool
-Microsoft.AspNetCore.Components.WebAssembly.Server.WebAssemblyComponentsEndpointOptions.ServeMultithreadingHeaders.set -> void
 Microsoft.AspNetCore.Components.WebAssembly.Server.WebAssemblyComponentsEndpointOptions.StaticAssetsManifestPath.get -> string?
 Microsoft.AspNetCore.Components.WebAssembly.Server.WebAssemblyComponentsEndpointOptions.StaticAssetsManifestPath.set -> void
 static Microsoft.Extensions.DependencyInjection.WebAssemblyRazorComponentsBuilderExtensions.AddAuthenticationStateSerialization(this Microsoft.Extensions.DependencyInjection.IRazorComponentsBuilder! builder, System.Action<Microsoft.AspNetCore.Components.WebAssembly.Server.AuthenticationStateSerializationOptions!>? configure = null) -> Microsoft.Extensions.DependencyInjection.IRazorComponentsBuilder!