WooCommerce Catalog Visibility Options 3.3.4

* Update: Validate WC() is not null before setting sessions. Apparently some plugins cause issues with the WC() instance.
* Update: Correct previous publish date.
* Update: Check for correct WooCommerce class name in session handler.

* Update: Filter WooCommerce related products query.
* Update: Added basic caching on the restrictions look up.
* Update: Remove legacy filtering code.
* Update: Added filters to filter products rendered using the AbstractProductGrid class, notably Gutenberg product blocks.
* Update: Unbind filters before WooCommerce generates emails. It appears that some payment gateways mistakenly call the price_html filters somehow during
the email process, therefore catalog visibility options filters it out.
* Update session handling code to prevent extensions from calling init without WC being loaded.

* Update: Remove deprecated function calls for WC 3.6