Removes the bulk product update feature and its associated components:
- Removes Angular-based bulk product editing controller and views
- Deletes bulk product API endpoints and related controller actions
- Removes product cloning and variant deletion functionality
- Removes associated JavaScript tests and specs
This appears to be part of a larger effort to modernize/simplify the product management interface, removing legacy Angular-based bulk editing in favor of a different approach.
Extracts the JSON response from the admin's line item controller which
are only used by the bulk management feature into its own controller.
This decouples spree from an OFN-only feature and allows to remove
unnecessary code. Furthermore, Admin::LineItemsController is gone in
Spree 2.4.0.beta. See: https://github.com/spree/spree/pull/5280
