Simplify using helper methods in components

The `use_helpers` method was added in ViewComponent 3.8.0, and it's
included by default in all components since version 3.11.0.

Note we sometimes delegated the `can?` method to the controller instead
of the helpers, for no particularly reason. We're unifying that code as
well.

app/components/application_component.rb

@@ -1,5 +1,5 @@
 class ApplicationComponent < ViewComponent::Base
   include SettingsHelper
-  delegate :back_link_to, :t, to: :helpers
+  use_helpers :back_link_to, :t
   delegate :default_form_builder, to: :controller
 end