Add [Obsolete] attribute to WebHost class with suppression pragmas

Co-authored-by: BrennanConroy <[email protected]>

Author: Copilot

src/Hosting/Hosting/src/Internal/WebHost.cs

@@ -19,6 +19,7 @@
 
 namespace Microsoft.AspNetCore.Hosting;
 
+[Obsolete("WebHost is obsolete. Use HostBuilder or WebApplicationBuilder instead.")]
 internal sealed partial class WebHost : IWebHost, IAsyncDisposable
 {
     private const string DeprecatedServerUrlsKey = "server.urls";

src/Hosting/Hosting/src/WebHostBuilder.cs

@@ -160,12 +160,14 @@ public IWebHost Build()
 
         AddApplicationServices(applicationServices, hostingServiceProvider);
 
+#pragma warning disable CS0618 // Type or member is obsolete
         var host = new WebHost(
             applicationServices,
             hostingServiceProvider,
             _options,
             _config,
             hostingStartupErrors);
+#pragma warning restore CS0618 // Type or member is obsolete
         try
         {
             host.Initialize();