Added Unified connection support (#3785)

* Added Unified connection support

* Use generic way to do expandNode.
Cleanup the ported code and removed unreference code. Added as needed later.
Resolved PR comments.

* Minor fixes and removed timer for all expanders for now. If any providers can't response, the tree node will spin and wait. We may improve later.

* Change handSessionClose to not thenable.
Added a node to OE to show error message instead of reject. So we could show partial expanded result if get any.
Resolve PR comments

* Minor fixes of PR comments

extensions/mssql/src/utils.ts

@@ -4,6 +4,8 @@
  *--------------------------------------------------------------------------------------------*/
 'use strict';
 
+import * as sqlops from 'sqlops';
+
 import * as path from 'path';
 import * as crypto from 'crypto';
 import * as os from 'os';
@@ -169,3 +171,15 @@ export function verifyPlatform(): Thenable<boolean> {
 		return Promise.resolve(true);
 	}
 }
+
+export function getErrorMessage(error: Error | string): string {
+	return (error instanceof Error) ? error.message : error;
+}
+
+export function isObjectExplorerContext(object: any): object is sqlops.ObjectExplorerContext {
+	return 'connectionProfile' in object && 'isConnectionNode' in object;
+}
+
+export function getUserHome(): string {
+	return process.env.HOME || process.env.USERPROFILE;
+}