Infinite loop in ConfigurableLanguageManager->getLanguages() on language config entities import

This issue is based on a bug found when using the Configuration installer contrib module : #2623878: The "configurable_language" entity type does not exist.. It looks like a core bug to me, which might happen in other configuration imports use cases. Sorry if I'm wrong.

A comment in ConfigurableLanguageManager->getLanguages() mentions :

// Load configurable languages on top of the defaults. Ideally this could
// use the entity API to load and instantiate ConfigurableLanguage
// objects. However the entity API depends on the language system, so that
// would result in infinite loops. We use the configuration system
// directly and instantiate runtime Language objects. When language
// entities are imported those cover the default and locked languages, so
// site-specific configuration will prevail over the fallback values.
// Having them in the array already ensures if this is invoked in the
// middle of importing language configuration entities, the defaults are
// always present.

Unfortunately, infinite loops can still happen, at least in my use case. The languages sort needs the languages names, which need getLanguages() again to get translated, etc. I have no idea where the loop should be broken.

Here's the loop (you can see the full calls tree in #2623878: The "configurable_language" entity type does not exist.).

222.75179744536Drupal\language\ConfigurableLanguageManager->getLanguages(  )../language.module:286


232.75379751024Drupal\Core\Language\Language::sort(  )../ConfigurableLanguageManager.php:319
242.75379751432uasort
(  )../Language.php:157
252.75379751560Drupal\Core\Language\Language::Drupal\Core\Language\{closure}(  )../Language.php:157
262.75379751640strnatcasecmp
(  )../Language.php:154
272.75379751824Drupal\Core\StringTranslation\TranslatableMarkup->__toString(  )../Language.php:154
282.75379751968Drupal\Core\StringTranslation\TranslatableMarkup->render(  )../ToStringTrait.php:20
292.75379752080Drupal\Core\StringTranslation\TranslationManager->translateString(  )../TranslatableMarkup.php:204
302.75379752224Drupal\Core\StringTranslation\TranslationManager->doTranslate(  )../TranslationManager.php:119
312.75379752784Drupal\Core\StringTranslation\TranslationManager->getStringTranslation(  )../TranslationManager.php:147
322.75389754048Drupal\locale\LocaleTranslation->getStringTranslation(  )../TranslationManager.php:99
332.75409767672Drupal\Core\Cache\CacheCollector->get(  )../LocaleTranslation.php:123
342.75449788040Drupal\locale\LocaleLookup->resolveCacheMiss(  )../CacheCollector.php:153
352.78329821016Drupal\language\ConfigurableLanguageManager->getFallbackCandidates(  )../LocaleLookup.php:163
362.78329821016Drupal\language\ConfigurableLanguageManager->isMultilingual(  )../ConfigurableLanguageManager.php:372
372.78339821064Drupal\language\ConfigurableLanguageManager->getLanguages(  )../ConfigurableLanguageManager.php:149
382.78359823976Drupal\Core\Language\Language::sort(  )../ConfigurableLanguageManager.php:319
392.78359824384uasort

I can easily make Xdebug breakpoints on it if needed, as the same infinite loop happens when I try to load any page of my not-fully-imported website.
After $languages += $this->getDefaultLockedLanguages($default->getWeight()); instruction, $languages in an array with und, zxx, and fr. One line after that, $config_ids is set to

Array
(
    [0] => language.entity.fr
    [1] => language.entity.und
)

This is because language.entity.zxx.yml it not yet imported. So that on Language::sort($languages); instruction, $languages[$langcode]->name is a string for fr and und, but for zxx the name is still a TranslatableMarkup object, so that the sort will call __toString() on it.