Extend DefaultI18NProvider for Spring

[caalador]

For spring there should be a Bean defined for DefaultI18NProvider that would check for default translations using ResourcePatternResolver e.g. resourcePatternResolver.getResources("classpath:**/vaadin-i18n/*.properties);

Code would be something like:

@Bean
@ConditionalOnMissingBean(value = I18NProvider.class)
public DefaultI18NProvider vaadinI18nProvider() {
  Resource[] translations = resourcePatternResolver.getResources("classpath:**/vaadin-i18n/*.properties);
  if(translations.length > 0) {
    List<Locale> locales = I18NUtil.collectLocalesFromFiles(Arrays.stream(translations).map(Resource::getFile).collect(Collectors.toList()));
    return new DefaultI18NProvider(locales );
  }
  return null;
}

I18NUtil needs extraction of the collectLocalesFromFiles.

Continuation of #17823 and #5917

[vaadin-bot]

This ticket/PR has been released with Vaadin 24.3.0.alpha4 and is also targeting the upcoming stable 24.3.0 version.