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.Hosting.UnitTests/ProtocolTests/EventContextTests.cs

@@ -0,0 +1,32 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Collections.Concurrent;
+using System.Linq;
+using Microsoft.SqlTools.Hosting.Protocol;
+using NUnit.Framework;
+
+namespace Microsoft.SqlTools.Hosting.UnitTests.ProtocolTests
+{
+    [TestFixture]
+    public class EventContextTests
+    {
+        [Test]
+        public void SendEvent()
+        {
+            // Setup: Create collection
+            var bc = new BlockingCollection<Message>(new ConcurrentQueue<Message>());
+
+            // If: I construct an event context with a message writer
+            //     And send an event with it
+            var eventContext = new EventContext(bc);
+            eventContext.SendEvent(CommonObjects.EventType, CommonObjects.TestMessageContents.DefaultInstance);
+
+            // Then: The message should be added to the queue
+            var messages = bc.ToArray().Select(m => m.MessageType);
+            Assert.That(messages, Is.EqualTo(new[] { MessageType.Event }), "Single message of type event in the queue after SendEvent");
+        }
+    }
+}