WooCommerce Composite Products 10.4.0

* Feature - Re-introduce 'Virtual' checkbox for Composite Products. When saving a Composite as Virtual, all physical products purchased in its Components will be treated as Virtual, too.
* Fix - Fixed 'Undefined variable: availability' notice in 'WC_CP_Product::get_availability_text()'.
* Fix - Display the component page with the selected option on page load for paginated components.
* Tweak - Updated the data structure returned by 'WC_CP_Scenarios_Manager::get_settings()' to prevent datatype errors when 'json_encode' gets called downstream.
* Tweak - Added 'add-to-cart' parameter to submit button.

* Fix - Reset product ordering query filters after querying component options.
* Fix - Hide stock message for composited products on backorder.
* Fix - Fixed some styling issues with the Astra theme.
* Fix - Fixed Composite Summary Widget styling issues on small screen sizes.
* Fix - Fixed Composite Summary Widget styling issues with the Divi theme.
* Fix - Fixed Composite Summary Widget styling issues with the TwentyTwenty theme and Elementor Pro.
* Fix - Autoscrolling to the current selection now works for all Components when using the Stacked layout.

* Tweak - Removed deprecated 'woocommerce_add_to_[cart/order]_validation' filter.
* Fix - Stopped requiring 'configuration' property in 'composite_scenarios' field items to permit deletions.