Fix custom locales not taking precedence

When we upgraded to Rails 7 in commit 8596f1539, we broke the custom
locales since now all nested folders in `config/locales/` are loaded by
default [1]. This meant that the custom folder was now loaded before any
languages whose code alphabetically goes after the word "custom".

As a workaround, we're overwriting the default locales paths so they
don't include the custom folder. We're doing this step before the
`add_locales` initializer; that is, before the default locales paths are
used.

Unfortunately, I haven't found a way to add a test for this behavior,
since we would need to add a file in `config/locales/custom` that
overwrites an internationalization key for an existing language, but
only during a specific test, and the i18n load path is evaluated when
the application starts up.

[1] See pull request 41872 in https://github.com/rails/rails/

config/application.rb

@@ -113,7 +113,9 @@ module Consul
       "val" => "es"
     }]
 
-    config.i18n.load_path += Dir[Rails.root.join("config", "locales", "**[^custom]*", "*.{rb,yml}")]
+    initializer :exclude_custom_locales_automatic_loading, before: :add_locales do
+      paths.add "config/locales", glob: "**[^custom]*/*.{rb,yml}"
+    end
     config.i18n.load_path += Dir[Rails.root.join("config", "locales", "custom", "**", "*.{rb,yml}")]
 
     config.after_initialize do