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/ChannelBase.cs

@@ -0,0 +1,58 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Threading.Tasks;
+using Microsoft.SqlTools.Hosting.Protocol;
+
+namespace Microsoft.SqlTools.Hosting.Channels
+{
+    /// <summary>
+    /// Defines a base implementation for servers and their clients over a
+    /// single kind of communication channel.
+    /// </summary>
+    public abstract class ChannelBase
+    {
+        #region Properties 
+        
+        /// <summary>
+        /// Gets a boolean that is true if the channel is connected or false if not.
+        /// </summary>
+        public bool IsConnected { get; protected internal set; }
+
+        /// <summary>
+        /// Gets the MessageReader for reading messages from the channel.
+        /// </summary>
+        public MessageReader MessageReader { get; protected internal set; }
+
+        /// <summary>
+        /// Gets the MessageWriter for writing messages to the channel.
+        /// </summary>
+        public MessageWriter MessageWriter { get; protected internal set; }
+        
+        #endregion
+        
+        #region Abstract Methods
+
+        /// <summary>
+        /// Starts the channel and initializes the MessageDispatcher.
+        /// </summary>
+        public abstract void Start();
+
+        /// <summary>
+        /// Stops the channel.
+        /// </summary>
+        public abstract void Stop();
+        
+        /// <summary>
+        /// Returns a Task that allows the consumer of the ChannelBase
+        /// implementation to wait until a connection has been made to
+        /// the opposite endpoint whether it's a client or server.
+        /// </summary>
+        /// <returns>A Task to be awaited until a connection is made.</returns>
+        public abstract Task WaitForConnection();
+        
+        #endregion
+    }
+}