Support HDFS Tiering (#7484)

This is the 1st step to supporting HDFS Tiering
Changes:

Add new mounted folder icon. Will have separate commit for file icon
Disable delete/mkdir/upload for mounted files and folders
Disable delete for root HDFS folder (this was added in error)

extensions/mssql/src/hdfs/mount.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.
+ *--------------------------------------------------------------------------------------------*/
+
+/**
+ * Information about a HDFS mount to a remote directory
+ */
+export interface Mount {
+	mountPath: string;
+	mountStatus: string;
+	remotePath: string;
+}
+
+export enum MountStatus {
+	None = 0,
+	Mount = 1,
+	Mount_Child = 2
+}

extensions/mssql/src/hdfs/webhdfs.ts

@@ -12,6 +12,7 @@ import * as nls from 'vscode-nls';
 import * as auth from '../util/auth';
 import { IHdfsOptions, IRequestParams } from '../objectExplorerNodeProvider/fileSources';
 import { IAclStatus, AclEntry, parseAcl, AclPermissionType, parseAclPermissionFromOctal, AclEntryScope } from './aclEntry';
+import { Mount } from './mount';
 import { everyoneName } from '../localizedConstants';
 
 const localize = nls.loadMessageBundle();
@@ -472,6 +473,26 @@ export class WebHDFS {
 		});
 	}
 
+	/**
+	 * Get all mounts for a HDFS connection
+	 * @param callback Callback to handle the response
+	 * @returns void
+	 */
+	public getMounts(callback: (error: HdfsError, mounts: Mount[]) => void): void {
+		let endpoint = this.getOperationEndpoint('listmounts', '');
+		this.sendRequest('GET', endpoint, undefined, (error, response) => {
+			if (!callback) { return; }
+			if (error) {
+				callback(error, undefined);
+			} else if (response.body.hasOwnProperty('Mounts')) {
+				const mounts = response.body.Mounts;
+				callback(undefined, mounts);
+			} else {
+				callback(new HdfsError(ErrorMessageInvalidDataStructure), undefined);
+			}
+		});
+	}
+
 	/**
 	 * Check file existence
 	 * Wraps stat method