EE application settings (not Docs) Cleanup

What does this MR do?

Note: Ports https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20723 to EE (Attempts to, anyways). Merge this (EE) first.

As part of https://gitlab.com/gitlab-org/gitlab-ce/issues/49155, this is a small cleanup so that the docs and settings sync better together. Mostly alphabetizing, but a few typo fixes too.

Fixed in settings.rb:

• Typo in sidekiq_throttling_queus to sidekiq_throttling_queues
• Typo in performance_bar_allowed_group_id description (Depreated -> Deprecated)

Alphabetized: settings.rb application_setting.rb application_settings_helper.rb ee/app/helpers/ee/application_settings_helper.rb and ee/app/models/ee/application_setting.rb

To Check:

• encrypted_external_auth_client_key
• encrypted_external_auth_client_key_iv
• encrypted_external_auth_client_key_pass
• encrypted_external_auth_client_key_pass_iv

Related to: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20721 https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20723 https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/6600

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?