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.DataProtocol.Contracts/Common/WorkspaceFolder.cs

@@ -0,0 +1,20 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+namespace Microsoft.SqlTools.DataProtocol.Contracts.Common
+{
+    public class WorkspaceFolder
+    {
+        /// <summary>
+        /// Name of the workspace folder. Defaults to <see cref="Uri"/>'s basename
+        /// </summary>
+        public string Name { get; set; }
+        
+        /// <summary>
+        /// Associated URI for this workspace folder
+        /// </summary>
+        public string Uri { get; set; }
+    }
+}