WooCommerce Pre-Orders 2.1.0

* Add - Order types filter in the order list when HPOS is enabled.
* Add - Implement support for automatic translation files delivery.
* Fix - Improve failed pre-order status transition logic.
* Fix - Countdown timer output issue.
* Dev - Bump PHP minimum supported version from 7.0 to 7.2.
* Dev - Bump WooCommerce minimum supported version from 6.0 to 6.8.
* Dev - Bump WooCommerce "tested up to" version 7.4.
* Dev - Export _wc_pre_orders_availability_datetime metadata in human readable date format (mysql format).

* Add - Support for High-performance Order Storage ("HPOS") (formerly known as Custom Order Tables, "COT").
* Add - Declare compatibility with High-Performance Order Storage ("HPOS").
* Fix - Ensure custom messages get added to the pre-order completion email.
* Fix - Improve variable type checking.
* Fix - Set correct order status to when complete payment for failed pre-order.
* Tweak - Bump minimum WP version to 5.6.
* Tweak - Bump minimum PHP version to 7.0.
* Tweak - Bump minimum WC version to 6.0.

* Tweak – Switch to global functions to remove deprecation warnings coming from WooCommerce Blocks.
* Fix – Ensure store admins receive notifications of any pre-order cancellations.
* Add – New column to the Pre-Orders admin table to show the linked order status.