Slightly reduce RAM usage (#7301)

* 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

app/workers/scheduler/ip_cleanup_scheduler.rb

@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-require 'sidekiq-scheduler'
 
 class Scheduler::IpCleanupScheduler
   include Sidekiq::Worker