Refactor admin notices

[bilfeldt]

The current way we show admin noticed (used for bulk action) can be refactored to:

• Use the Wordpress Transients API instead of using session or settings in DB
• Use the WooCommerce WC_Admin_Notices API (note there is also a customer facing Woocommerce wc_notice version)
• Use a trait or a dedicated class (see this implementation) for pushing and retrieving the noticed.
• Add a query parameter to the redirect url to indicate that it has been processed by the plugin. That way we only need to check for new noticed when that query parameter is set.

Note that there is also WordPress Admin notices but the above WooCommerce option is preferred.