Add ModelContextProtocol.AspNetCore (#160)

* Add ModelContextProtocol.AspNetCore

- Remove IServerTransport and HttpListenerSseServerTransport
- Replace HttpListenerSseServerTransport usage in tests with ASP.NET Core.

Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
Co-authored-by: Jeff Handley <jeffhandley@users.noreply.github.com>

samples/AspNetCoreSseServer/Program.cs

@@ -1,10 +1,9 @@
-using AspNetCoreSseServer;
+using ModelContextProtocol.AspNetCore;
 
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddMcpServer().WithToolsFromAssembly();
 var app = builder.Build();
 
-app.MapGet("/", () => "Hello World!");
-app.MapMcpSse();
+app.MapMcp();
 
 app.Run();