Beta updates for HPOS support

[smolentzov-stripe]

WooCommerce is introducing High Performance Order Storage (HPOS) to optimize its database for eCommerce needs: https://woocommerce.com/document/high-performance-order-storage/ Per WooCommerce: "It uses the WooCommerce CRUD design to store order data in custom tables – optimized for WooCommerce queries with minimal impact on the store’s performance." The TaxJar WooCommerce plugin was already largely using the WooCommerce CRUD tables.

This PR:

• Makes some small changes to places where the database was being directly queried, to support using either the old WordPress tables, or the new WooCommerce tables.
• Marks the TaxJar plugin as being compatible with HPOS so that the feature can be enabled.
• Updates the tests to support some changes around PHPUnit: https://make.wordpress.org/core/2021/09/27/changes-to-the-wordpress-core-php-test-suite/

Steps to Reproduce Enable High-Performance Order Storage as described here: https://woocommerce.com/document/high-performance-order-storage/ Switch over to “Use WooCommerce order tables” and “Keep the post tables and the order tables synchronized”.

Expected Result Test common store functions and ensure normal behavior. Order creation, sales tax calculation, and syncing to your TaxJar account should all work as normal.

Click-Test Versions

• [x] Woo 7.8
• [x] Woo 7.4
• [x] Woo 7.1

Specs Passing

• [x] Woo 7.8
• [x] Woo 7.4
• [x] Woo 7.1

Note that the feature flag to enable HPOS was introduced in WooCommerce version 7.1: https://developer.woocommerce.com/2022/11/08/woocommerce-7-1-0-released/

[a432511]

Nice work! Do you know when this will be released? @smolentzov-stripe