Ensure all ApplicationSettings attributes have a corresponding `config/application_setting_columns/*.yml` file

The following discussion from !166509 (merged) should be addressed:

• @alexpooley started a discussion: (+1 comment)

  @rymai are the clusterwide columns in https://main-ee-166509.docs.gitlab-review.app/ee/development/cells/application_settings_analysis.html manually defined? Are the current values settings you have worked through yourself?

  What happens when a new setting is added/deleted? Maybe we can add a spec to force devs to run the script? We have added similar processes elsewhere. Something like...

  it `has a doc file for application setting` do
    for each application setting column
      cross reference with file in db/docs/application_settings/
      fail with update instructions if file doesn't exist
  
  it `has an application setting for each doc file' do
    for each file in db/docs/application_settings/
      cross reference with application setting column
      fail with delete db doc instructions if column does not exist