We'd like to use it for FIDO2 tokens too, and the concept is entirely
generic, hence let's just reuse the field, but rename it. Read the old
name for compatibility, and treat the old name and the new name as
identical for most purposes.
Make use of the new user_record_build_image_path() helper the previous
commit added to share some code.
Also, let's make sure we update all parsed-out fields with the new data
from the binding, so that the parsed-out fields are definitely
up-to-date.
