Return the right cache contexts from the price formatters

Once 📌 Convert the country and locale resolvers to return value objects Fixed and 📌 Create a country cache context Fixed are done, the price formatters should return the language and country contexts.

That needs to look something like this:

$elements[$delta] = [
  '#cache' => [
    'contexts' => [
       'languages:' . LanguageInterface::TYPE_INTERFACE,
        'country',
    ],
  ],