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/RetryCallbackEventArgs.cs

@@ -0,0 +1,61 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+// This code is copied from the source described in the comment below.
+
+// =======================================================================================
+// Microsoft Windows Server AppFabric Customer Advisory Team (CAT) Best Practices Series
+//
+// This sample is supplemental to the technical guidance published on the community
+// blog at http://blogs.msdn.com/appfabriccat/ and  copied from
+// sqlmain ./sql/manageability/mfx/common/
+//
+// =======================================================================================
+// Copyright © 2012 Microsoft Corporation. All rights reserved.
+// 
+// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER 
+// EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF 
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. YOU BEAR THE RISK OF USING IT.
+// =======================================================================================
+
+// namespace Microsoft.SQL.CAT.BestPractices.SqlAzure.Framework
+// namespace Microsoft.SqlServer.Management.Common
+
+using System;
+
+namespace Microsoft.SqlTools.CoreServices.Connection.ReliableConnection
+{
+    /// <summary>
+    /// Defines a arguments for event handler which will be invoked whenever a retry condition is encountered.
+    /// </summary>
+    internal sealed class RetryCallbackEventArgs : EventArgs
+    {
+        private readonly int _retryCount;
+        private readonly Exception _exception;
+        private readonly TimeSpan _delay;
+
+        public RetryCallbackEventArgs(int retryCount, Exception exception, TimeSpan delay)
+        {
+            _retryCount = retryCount;
+            _exception = exception;
+            _delay = delay;
+        }
+
+        public TimeSpan Delay
+        {
+            get { return _delay; }
+        } 
+
+        public Exception Exception
+        {
+            get { return _exception; }
+        }
+
+        public int RetryCount
+        {
+            get { return _retryCount; }
+        }
+    }
+}