feat: Translate collection GETs per item

Lauri Timmaneerequested to merge
issue/jsonapi_multilingual-3612345:3612345-translate-collection-gets into 1.0.x

This diverges from #3199697 which targets a translation on individual resources only. This translates every item of a collection from the same langCode / Accept-Language contract, via the EntityAccessChecker::getEntityTranslation() seam that core already calls for each collection item. A strict langCode returns only items that have the translation (getCollectionQuery adds a langcode condition); Accept-Language falls back to the default per item.

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

Closes #3612345

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