WooCommerce Recommendation Engine 3.5.1

* Update: WC and WP compatibility updates
* Update: Remove legacy code that was used to support older versions of WooCommerce.
* Update: Remove some deprecation notices related to strpos and str_replace functions.

Fix: Tweaks to the enhanced security to format HTML properly.

* Fix: Fix one remaining issue with the legacy code which was used to support older versions of WC.
* Updates: Updates to satisfy the security scanner.

* Update: WC and WP Updates.
* Update: HPOS compatibility.
* Fix: Correctly sort the Recommended Widget by the correct direction when using the "Also Viewed" type.