Reduce DuplicateJobs Redis workload

We know from experience (e.g. #925 (comment 1049551083)) that the DuplicateJobs Sidekiq middleware adds a considerable amount of CPU load to redis-sidekiq. I suspect that we can optimize the Redis calls we are making and I want to investigate this in this issue.

Status 2022-11-22

We have seen steady utilization not exceeding 40% for 2.5 weeks now. TamLand is still incorrectly forecasting a downward trend, we are not waiting for it to correct itself.