Delay usage of get_plugin_name() in payment gateway privacy class to after init

[agibson-godaddy]

Release: #763

Summary

This is another change to fix "translations loaded too early". This impacts plugins that use the privacy class. It delays some of the logic until after init. I followed WooCommerce core's lead a bit here: https://github.com/woocommerce/woocommerce/blob/trunk/plugins/woocommerce/includes/class-wc-privacy.php#L32-L36

Details

QA

1. Update a payment gateway plugin to use this branch -- e.g. https://github.com/gdcorp-partners/woocommerce-gateway-authorize-net-cim/pull/113
2. Go to Tools > Export Personal Data and submit an export for someone who has placed an order with that gateway.
3. Download the file.
4. Open the index.html file
   • You see "Authorize.Net Credit Card Payment Tokens" at the top
5. Click it
   • Data is present

Before merge

• I have confirmed these changes in each supported minor WooCommerce version