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/RetryState.cs

@@ -0,0 +1,86 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+
+namespace Microsoft.SqlTools.CoreServices.Connection.ReliableConnection
+{
+    internal class RetryState 
+    {
+        private int _retryCount = 0;
+        private TimeSpan _delay = TimeSpan.Zero;
+        private Exception _lastError = null;
+        private bool _isDelayDisabled = false;
+
+        /// <summary>
+        /// Gets or sets the current retry attempt count.
+        /// </summary>
+        public int RetryCount 
+        {
+            get
+            {
+                return _retryCount;
+            }
+            set
+            {
+                _retryCount = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the delay indicating how long the current thread will be suspended for before the next iteration will be invoked.
+        /// </summary>
+        public TimeSpan Delay 
+        {
+            get
+            {
+                return _delay;
+            }
+            set
+            {
+                _delay = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the exception which caused the retry conditions to occur.
+        /// </summary>
+        public Exception LastError 
+        {
+            get
+            {
+                return _lastError;
+            }
+            set
+            {
+                _lastError = value;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether we should ignore delay in order to be able to execute our tests faster
+        /// </summary>
+        /// <remarks>Intended for test use ONLY</remarks>
+        internal bool IsDelayDisabled 
+        { 
+            get
+            {
+                return _isDelayDisabled;
+            }
+            set
+            {
+                _isDelayDisabled = value;
+            }
+        }
+
+        public virtual void Reset()
+        {
+            this.IsDelayDisabled = false;
+            this.RetryCount = 0;
+            this.Delay = TimeSpan.Zero;
+            this.LastError = null;
+        }
+    }
+}