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.CoreServices/Connection/ReliableConnection/DbCommandWrapper.cs

@@ -0,0 +1,71 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Data;
+using Microsoft.Data.SqlClient;
+using Microsoft.SqlTools.Hosting.Utility;
+
+namespace Microsoft.SqlTools.CoreServices.Connection.ReliableConnection
+{
+
+    /// <summary>
+    /// Wraps <see cref="IDbCommand"/> objects that could be a <see cref="SqlCommand"/> or
+    /// a <see cref="ReliableSqlConnection.ReliableSqlCommand"/>, providing common methods across both.
+    /// </summary>
+    internal sealed class DbCommandWrapper
+    {
+        private readonly IDbCommand _command;
+        private readonly bool _isReliableCommand;
+
+        public DbCommandWrapper(IDbCommand command)
+        {
+            Validate.IsNotNull(nameof(command), command);
+            if (command is ReliableSqlConnection.ReliableSqlCommand)
+            {
+                _isReliableCommand = true;
+            }
+            else if (!(command is SqlCommand))
+            {
+                throw new InvalidOperationException(Resources.InvalidCommandType);
+            }
+            _command = command;
+        }
+
+        public static bool IsSupportedCommand(IDbCommand command)
+        {
+            return command is ReliableSqlConnection.ReliableSqlCommand
+                || command is SqlCommand;
+        }
+
+
+        public event StatementCompletedEventHandler StatementCompleted
+        {
+            add
+            {
+                SqlCommand sqlCommand = GetAsSqlCommand();
+                sqlCommand.StatementCompleted += value;
+            }
+            remove
+            {
+                SqlCommand sqlCommand = GetAsSqlCommand();
+                sqlCommand.StatementCompleted -= value;
+            }
+        }
+
+        /// <summary>
+        /// Gets this as a SqlCommand by casting (if we know it is actually a SqlCommand)
+        /// or by getting the underlying command (if it's a ReliableSqlCommand)
+        /// </summary>
+        private SqlCommand GetAsSqlCommand()
+        {
+            if (_isReliableCommand)
+            {
+                return ((ReliableSqlConnection.ReliableSqlCommand) _command).GetUnderlyingCommand();
+            }
+            return (SqlCommand) _command;
+        }
+    }
+}