Enable netfx testing. (#588)

* Enable netfx testing.

* Skip impacted tests and re-enable netfx testing.

* Remove redundant comment.

* Remove unnecessary project configuration.

* Simplify test server copying.

src/ModelContextProtocol.Core/Server/StreamServerTransport.cs

@@ -46,7 +46,11 @@ public class StreamServerTransport : TransportBase
 
         _logger = loggerFactory?.CreateLogger(GetType()) ?? NullLogger.Instance;
 
+#if NET
         _inputReader = new StreamReader(inputStream, Encoding.UTF8);
+#else
+        _inputReader = new CancellableStreamReader(inputStream, Encoding.UTF8);
+#endif
         _outputStream = outputStream;
 
         SetConnected();