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

config/initializers/json_ld.rb

@@ -1,5 +0,0 @@
-# frozen_string_literal: true
-
-require_relative '../../lib/json_ld/identity'
-require_relative '../../lib/json_ld/security'
-require_relative '../../lib/json_ld/activitystreams'

config/initializers/oembed.rb

@@ -1,4 +0,0 @@
-# frozen_string_literal: true
-
-require_relative '../../app/lib/provider_discovery'
-OEmbed::Providers.register_fallback(ProviderDiscovery)