WooCommerce Catalog Visibility Options 3.3.4

* Update: WP and WC version compatibility.

Update: WP and WC version compatibility.
* Update: Move clearing of transients into a separate class so it can be queued and called during shutdown.
* Update: Remove legacy code for WC 2.6 and older.
* Update: Remove legacy code regarding extension updates and WC active check.
* Update: General code cleanup.

* Update: WP and WC version compatibility.
* Update: Call catalog_visibility_alternate_add_to_cart_link_url filter on the add to cart link for shop links.
* New: Allow filtering of the locations which are used for the location picker. Use the filter woocommerce_catalog_restrictions_available_locations.
* add_filter( 'woocommerce_catalog_restrictions_available_locations', function( $available_locations, $allowed_countries, $allowed_states, $use_states ) {
* $available_locations = [
* 'US' => [
* 'title' => 'United States',
* 'code' => 'US',