WooCommerce Square Payment Gateway 4.9.1

* Fix - Inconsistency in the height of Express Payment Button and compliance with the new Woo Express Payment Method Styling API.
* Fix - Ensure the "Uncaught TypeError" JavaScript console error does not occur for out-of-stock products.
* Fix - Ensure compatibility with WooPayments extension.
* Dev - Bump WooCommerce "tested up to" version 9.1.
* Dev - Bump WooCommerce minimum supported version to 8.9.
* Dev - Update NPM packages and node version to v20 to modernize developer experience.

* Fix - Check if dependencies are loaded before showing onboarding process.
* Fix - Ensure the product category syncs properly between the Square and WooCommerce store.
* Dev - Fix QIT E2E tests and add support for a few new test types.

* Fix - Remove double encoding from the redirect_url param in the oauth connect url.
* Dev - Bump WordPress "tested up to" version 6.6.