Fix background jobs not using locks like they are supposed to (#13361)

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

config/routes.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'sidekiq/web'
+require 'sidekiq_unique_jobs/web'
 require 'sidekiq-scheduler/web'
 
 Sidekiq::Web.set :session_secret, Rails.application.secrets[:secret_key_base]