Initial AD support for BDCs (#6741)

Partially working AD support for BDCs with some known issues
- Plumbed through kerberos support to Notebooks.
  - Using "gateway-0" for service temporarily as service endpoints API doesn't yet return correct DNS name. Will update in separate PR once available
- Plumbed kerberos auth to HDFS, Spark. Only partially working as we use same token on each call 
  - Will fix in separate PR, as this requires a refactor of WebHDFS library. Will need to either get new token every time or set a cookie, both of which require refactors
- Fixed error when Data Service node expansion failed and blocked all OE expansion
- Support for SqlToolsService change to use new cluster endpoints DMV
  -  Updated API to add new endpoints field to replace IP + port
  - Added logic to handle case where endpoints for Yarn, Grafana etc. are in the list
  - Sort list and use expected new localized strings

- Updated SqlToolsService to include support for new DMV
- Add "gateway-0" handling in Jupyter session as workaround for lack of domain names in endpoints list

extensions/mssql/src/util/auth.ts

@@ -0,0 +1,14 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as kerberos from 'kerberos';
+
+export async function authenticateKerberos(hostname: string): Promise<string> {
+	const service = 'HTTP' + (process.platform === 'win32' ? '/' : '@') + hostname;
+	const mechOID = kerberos.GSS_MECH_OID_KRB5;
+	let client = await kerberos.initializeClient(service, { mechOID });
+	let response = await client.step('');
+	return response;
+}