Add SQL Managed Instance support and sorting (#7996)

- Add SQL Instances folder and support using existing SQLClient API
- Sort subscriptions in tree and quickpick for easier search
- Sort all resources (Databases, Servers, Instances) alphabetically too

Not in this PR:
- Will experiment with Graph API for faster perf & easier addition of other Azure resources such as PostgreSQL

extensions/azurecore/src/azureResource/commands.ts

@@ -65,7 +65,7 @@ export function registerAzureResourceCommands(appContext: AppContext, tree: Azur
 				picked: selectedSubscriptionIds.indexOf(subscription.id) !== -1,
 				subscription: subscription
 			};
-		});
+		}).sort((a, b) => a.label.localeCompare(b.label));
 
 		const selectedSubscriptionQuickPickItems = (await window.showQuickPick(subscriptionQuickPickItems, { canPickMany: true }));
 		if (selectedSubscriptionQuickPickItems && selectedSubscriptionQuickPickItems.length > 0) {