Add extension api for calling azdata commands (#11763)

* Add extension api for calling azdata commands

* Update typings file name

extensions/azdata/src/typings/azdata-ext.d.ts

@@ -0,0 +1,51 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+/**
+ * Covers defining what the azdata extension exports to other extensions
+ *
+ * IMPORTANT: THIS IS NOT A HARD DEFINITION unlike vscode; therefore no enums or classes should be defined here
+ * (const enums get evaluated when typescript -> javascript so those are fine)
+ */
+export const enum extension {
+	name = 'Microsoft.azdata'
+}
+
+export interface SqlInstanceListResult {
+	clusterEndpoint: string,
+	externalEndpoint: string,
+	name: string,
+	status: string,
+	vCores: string
+}
+
+export interface PostgresServerListResult {
+	id: string,
+	clusterIP: string,
+	externalIP: string,
+	mustRestart: boolean,
+	name: string,
+	status: string
+}
+
+export interface AzdataOutput<R> {
+	logs: string[],
+	result: R[],
+	stderr: string[],
+	stdout: string[]
+}
+
+export interface IExtension {
+	postgres: {
+		server: {
+			list(): Promise<AzdataOutput<PostgresServerListResult>>
+		}
+	},
+	sql: {
+		instance: {
+			list(): Promise<AzdataOutput<SqlInstanceListResult>>
+		}
+	}
+}