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

src/sql/platform/connection/common/connectionManagementService.ts

@@ -1367,6 +1367,17 @@ export class ConnectionManagementService extends Disposable implements IConnecti
 		return credentials;
 	}
 
+	public getServerInfo(profileId: string): sqlops.ServerInfo {
+		let profile = this._connectionStatusManager.findConnectionByProfileId(profileId);
+		if (!profile) {
+			return undefined;
+		}
+
+		let serverInfo = profile.serverInfo;
+
+		return serverInfo;
+	}
+
 	/**
 	 * Get the connection string for the provided connection ID
 	 */