fix(upgrade): call setInterval outside the Angular zone

This wraps the $interval service when using upgrade to run the
$interval() call outside the Angular zone. However, the callback is
invoked within the Angular zone, so changes still propagate to
downgraded components.

packages/upgrade/src/common/constants.ts

@@ -11,6 +11,7 @@ export const $CONTROLLER = '$controller';
 export const $DELEGATE = '$delegate';
 export const $HTTP_BACKEND = '$httpBackend';
 export const $INJECTOR = '$injector';
+export const $INTERVAL = '$interval';
 export const $PARSE = '$parse';
 export const $PROVIDE = '$provide';
 export const $ROOT_SCOPE = '$rootScope';