Ensure _prefixes is not available as an action method on controllers

There was a change introduced in Rails 7.1 that causes all public
actions of non-abstract controllers to become action methods, even if
they happen to match the name of an internal method defined by abstract
`ActionController::Base` and such, which is the case with `_prefixes`.

This change was intentional, it allows for example to have an action
called `status`, which is an internal method, and that is properly
managed as an action method now. However, it broke Devise due to
overriding `_prefixes`, which is a public method of Action Controller.

To fix, we are simply ensuring we keep `_prefixes` as an internal method
rather than action method, which matches previous behavior for this
particular method/implementation in Devise.

Ref: rails/rails#48699

app/controllers/devise_controller.rb

@@ -33,6 +33,17 @@ def _prefixes #:nodoc:
     end
   end
 
+  # Override internal methods to exclude `_prefixes` since we override it above.
+  # There was an intentional change in Rails 7.1 that will allow it to become
+  # an action method because it's a public method of a non-abstract controller,
+  # but we also can't make this abstract because it can affect potential actions
+  # defined in the parent controller, so instead we ensure `_prefixes` is going
+  # to be considered internal. (and thus, won't become an action method.)
+  # Ref: https://github.com/rails/rails/pull/48699
+  def self.internal_methods #:nodoc:
+    super << :_prefixes
+  end
+
   protected
 
   # Gets the actual resource stored in the instance variable