Replace bootstrap methods with async factories

Controller.bootstrap and Host.bootstrap returned constructor arguments
that the caller had to spread into new Controller/Host, and
DatastoreProvider.bootstrap did the same for datastores. They are
replaced by Controller.fromConfig, Host.fromConfig and
KeyValueDatastore/SubscribableDatastore.fromProvider, which load the
data and return the finished instance.

Closes #1126

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/controller/controller.ts

@@ -147,15 +147,15 @@ async function handleBootstrapCommand(
 		path.join(databaseDirectory, "roles.json"),
 	);
 
-	const roles = new lib.SubscribableDatastore(...await new lib.JsonIdDatastoreProvider(
+	const roles = await lib.SubscribableDatastore.fromProvider(new lib.JsonIdDatastoreProvider(
 		path.join(databaseDirectory, "roles.json"),
 		lib.Role.fromJSON.bind(lib.Role),
-	).bootstrap());
+	));
 
-	const users = new lib.SubscribableDatastore(...await new lib.JsonIdDatastoreProvider(
+	const users = await lib.SubscribableDatastore.fromProvider(new lib.JsonIdDatastoreProvider(
 		path.join(databaseDirectory, "users.json"),
 		UserRecord.fromJSON.bind(UserRecord),
-	).bootstrap());
+	));
 
 	const userManager = new UserManager(users, roles, controllerConfig);
 
@@ -474,13 +474,12 @@ async function startup() {
 		return;
 	}
 
-	controller = new Controller(
+	controller = await Controller.fromConfig(
 		clusterLogger,
 		pluginInfos,
 		controllerConfig,
 		Boolean(args.canRestart),
 		Boolean(args.recovery),
-		...await Controller.bootstrap(controllerConfig)
 	);
 
 	// Refuse to start if there are no users loaded