Use custom translations in components

In the `i18n_translation` initializer, we're overwriting the `t` helper
so calling it uses custom translations if they're available.

However, ViewComponent doesn't use the `t` helper but implements its own
`t` method. So, when calling the `t` method in a component, we weren't
using our implementation of the `t` helper, and so we weren't loading
custom translations.

Using the `t` helper in components solves the issue.

There was a test where we were directly testing a method in a component,
and that method uses the `t` helper. This caused an error when running
the test:

ViewComponent::Base::ViewContextCalledBeforeRenderError:
`#helpers` can't be used during initialization, as it depends on the
view context that only exists once a ViewComponent is passed to the
Rails render pipeline.

Using `render_inline` in the test and testing the generated HTML, as
recommended in the ViewComponent documentation, solves the issue.

app/components/application_component.rb

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