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/ClientCapabilities/TextDocument/SignatureHelp.cs

@@ -0,0 +1,29 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.DataProtocol.Contracts.Common;
+
+namespace Microsoft.SqlTools.DataProtocol.Contracts.ClientCapabilities.TextDocument
+{
+    /// <summary>
+    /// Capabilities specific to textDocument/signatureHelp requests
+    /// </summary>
+    public class SignatureHelpCapabilities : DynamicRegistrationCapability
+    {           
+        /// <summary>
+        /// Client supports these SignatureInformation specific properties
+        /// </summary>
+        public SignatureInformationCapabilities SignatureInformation { get; set; }
+    }
+        
+    public class SignatureInformationCapabilities
+    {
+        /// <summary>
+        /// Client supports these content formats for the documentation property. The order
+        /// describes the preferred format of the client.
+        /// </summary>
+        public MarkupKind[] DocumentFormat { get; set; }
+    }
+}