Move unused forked code to external directory (#1192)

* Move unused forked code to external directory

* Fix SLN build errors

* Add back resource provider core since it's referenced by main resource provider project

* Update PackageProjects step of pipeline

external/Microsoft.SqlTools.Hosting.v2/Channels/StdioClientChannel.cs

@@ -0,0 +1,111 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.SqlTools.Hosting.Protocol;
+
+namespace Microsoft.SqlTools.Hosting.Channels
+{
+    /// <summary>
+    /// Provides a client implementation for the standard I/O channel.
+    /// Launches the server process and then attaches to its console
+    /// streams.
+    /// </summary>
+    public class StdioClientChannel : ChannelBase
+    {
+        private readonly string serviceProcessPath;
+        private readonly string serviceProcessArguments;
+
+        private Stream inputStream;
+        private Stream outputStream;
+        private Process serviceProcess;
+
+        /// <summary>
+        /// Initializes an instance of the StdioClient.
+        /// </summary>
+        /// <param name="serverProcessPath">The full path to the server process executable.</param>
+        /// <param name="serverProcessArguments">Optional arguments to pass to the service process executable.</param>
+        public StdioClientChannel(string serverProcessPath, params string[] serverProcessArguments)
+        {
+            serviceProcessPath = serverProcessPath;
+
+            if (serverProcessArguments != null)
+            {
+                serviceProcessArguments = string.Join(" ", serverProcessArguments);
+            }
+        }
+
+        public int ProcessId { get; private set; }
+        
+        public override void Start()
+        {
+            serviceProcess = new Process
+            {
+                StartInfo = new ProcessStartInfo
+                {
+                    FileName = serviceProcessPath,
+                    Arguments = serviceProcessArguments,
+                    CreateNoWindow = true,
+                    UseShellExecute = false,
+                    RedirectStandardInput = true,
+                    RedirectStandardOutput = true,
+                    RedirectStandardError = true,
+                    StandardOutputEncoding = Encoding.UTF8
+                },
+                EnableRaisingEvents = true
+            };
+
+            // Start the process
+            serviceProcess.Start();
+            ProcessId = serviceProcess.Id;
+
+            // Open the standard input/output streams
+            inputStream = serviceProcess.StandardOutput.BaseStream;
+            outputStream = serviceProcess.StandardInput.BaseStream;
+
+            // Set up the message reader and writer
+            MessageReader = new MessageReader(inputStream);
+            MessageWriter = new MessageWriter(outputStream);
+
+            IsConnected = true;
+        }
+
+        public override Task WaitForConnection()
+        {
+            // We're always connected immediately in the stdio channel
+            return Task.FromResult(true);
+        }
+
+        public override void Stop()
+        {
+            if (inputStream != null)
+            {
+                inputStream.Dispose();
+                inputStream = null;
+            }
+
+            if (outputStream != null)
+            {
+                outputStream.Dispose();
+                outputStream = null;
+            }
+
+            if (MessageReader != null)
+            {
+                MessageReader = null;
+            }
+
+            if (MessageWriter != null)
+            {
+                MessageWriter = null;
+            }
+
+            serviceProcess.Kill();
+        }
+    }
+}