* Fix Sidekiq warnings about JSON serialization
This occurs on every symbol argument we pass, and every symbol key in hashes,
because Sidekiq expects strings instead.
See https://github.com/mperham/sidekiq/pull/5071
We do not need to change how workers parse their arguments because this has
not changed and we were already converting to symbols adequately or using
`with_indifferent_access`.
* Set Sidekiq to raise on unsafe arguments in test mode
In order to more easily catch issues that would produce warnings in production
code.
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
* 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
Emelia Smith