LTI Adv: tag is not persisted during add external tool

Part of the LTI Advantage Assignment and Grade Services support, Moodle must retain for each grade item created for LTI the resource id and the tag as provided by the tool when the line item was created. The current implementation only retains the resource id.

1. The tag information is lost when the gradebook column is created as part of the external tool content creation

The proposed fix is:

1. Modify the add activity flow to pass both the tag as hidden input to the back end
2. have the back end create the associated gbs record with the tag