YITH WooCommerce PDF Invoice 4.16.0

* New: support for WooCommerce 8.6
* Update: YITH plugin framework
* Dev: added new filter yith_ywpi_product_item_metadata'
* Dev: added the yith_ywpi_apply_old_percentage_tax_calculation filter in the XML tax calculation
* Dev: added the placeholder parent_invoice_number in the document number block, to display the invoice number in the credit notes
* Dev: changed to public attribute
* Dev: minor change in a condition to check if the HPOS is enabled

* Update: YITH plugin framework
* Tweak: removed unnecessary conditions for the regular price retrieval in the invoices

* New: support for WooCommerce 8.5
* Update: YITH plugin framework
* Fix: fix issue with the invoice number generation generated by previous change
* Tweak: remove creation of the invoice when using the regeneration bulk action in an order doesn't have an invoice