Add datavirtualization extension (#21594)

* initial

* cleanup

* Add typings ref

* fix compile

* remove unused

* add missing

* another unused

* Use newer vscodetestcover

* newer dataprotocol

* format

* cleanup ignores

* fix out path

* fix entry point

* more cleanup

* Move into src folder

* Handle service client log messages

* remove unused

extensions/datavirtualization/src/test/testUtils.ts

@@ -0,0 +1,19 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as assert from 'assert';
+
+export async function assertThrowsAsync(fn: Function, msg: string): Promise<void> {
+	let f = () => {
+		// Empty
+	};
+	try {
+		await fn();
+	} catch (e) {
+		f = () => { throw e; };
+	} finally {
+		assert.throws(f, undefined, msg);
+	}
+}