This commit changes the behavior of the optin checkbox that MailPoet
adds to the WooCommerce checkout.
Now the checkbox is not checked by default for logged in users who
already subscribed to a list. Also, users won't be unsubscribed anymore
and have their global status change to unsubscribed if they uncheck the
checkbox.
The only action that is performed after this change is to subscribe
users if they check the checkbox.
This change was implemented both for the normal checkout and the block
checkout.
It was also necessary to remove the AutomateWoo integration that
depended on subscribers being unsubscribed during checkout.
[MAILPOET-4178]
The new namespace is supported from WooCommerce 6.4.0 so we don't need
to support the old namespace any more.
Some users reported issues with BC class aliases provided by Woo.
[MAILPOET-4774]
The current implementaiton of the deprecation of woocommerce_blocks_checkout_update_order_from_request
has a bug which causes a fatal error of our plugin. We do not want immediately switch to the
latest hook in order to keep older versions of the plugin compatible with MailPoet.
Therefore we switch to the deprecated __experimental ancestor for now.
[MAILPOET-4206]
