EntityConstraintViolationList::addAll doesn't reset groupings

Thanks for working on this @harivansh, this is looking great, just a couple of comments about the test - we need to call something to group the violations before we call addAll

Affects Experience Builder at 📌 Throw exceptions instead of returning tuples for validation errors Active — specifically at https://git.drupalcode.org/project/experience_builder/-/merge_requests/5....

(Not sure if that's where @larowlan discovered this bug? 🤔)