Also:

- Fix locks not being removed when jobs go to the dead job queue
- Add UI for managing locks to the Sidekiq dashboard
- Remove unused Sidekiq workers

Fix #13349

* Create Redisable

* Use #redis instead of Redis.current

* No need to re-require sidekiq plugins, they are required via Gemfile

* Add derailed_benchmarks tool, no need to require TTY gems in Gemfile

* Replace ruby-oembed with FetchOEmbedService

Reduce startup by 45382 allocated objects

* Remove preloaded JSON-LD in favour of caching HTTP responses

Reduce boot RAM by about 6 MiB

* Fix tests

* Fix test suite by stubbing out JSON-LD contexts

* When list is deleted, remove feed from redis

* Clean up list feeds of inactive users

* Clean up reblog-tracking sets from FeedManager

Builds on #5419, with a few minor optimizations and cleanup of sets
after they are no longer needed.

* Update tests, fix multiply-reblogged case

Previously, we would have lost the fact that a given status was
reblogged if the displayed reblog of it was removed, now we don't.

Also added tests to make sure FeedManager#trim cleans up our reblog
tracking keys, fixed up FeedCleanupScheduler to use the right loop,
and fixed the test for it.

* Keep references to all reblogs of a status on home feed

When inserting reblog: Add to set of reblogs of this status on
the feed, if original status was present in the feed, add it to
that set as well.

When removing a reblog: Remove it from that set. Take random
remaining item from the set. If one exists, re-insert it into feed,
otherwise do not re-insert anything.

Fix #4210

* When original is removed, toss out reblog references

* Add spec files for feed and media cleanup workers

* Add coverage for feed and media cleanup schedulers

* Clean up feed and media cleanup workers

sidekiq-scheduler jobs

Resolves #2495