Sidekiq: Evaluate the use of ActiveJob as a Sidekiq interactor - look for any gaps in instrumentation

[fallwith]

With #2195, we investigated instrumentation coverage for Sidekiq jobs' various perform* methods. A comment on that issue suggested the inclusion of perform_now as well. But perform_now and perform_later are ActiveJob-isms and were considered out of scope for #2195 and worthy of their own separate issue.

ActiveJob provides a standard way of interacting with job runners, Sidekiq included. We currently have test suites that utilize Sidekiq without Rails (without ActiveSupport even) and Rails without Sidekiq. We really ought to create a suite that blends the two and specifically uses perform_now and perform_later to kick off Sidekiq jobs. What instrumentation is produced in these scenarios? Is there ActiveSupport notifications driven instrumentation from the use of ActiveJob? Is the Sidekiq server middleware driven Sidekiq job instrumentation being engaged? Anything duplication overlap or any gaps in instrumentation coverage?

[workato-integration]

https://new-relic.atlassian.net/browse/NR-308504