Decide what to do with interface language for LANGCODE_NOT_APPLICABLE entities

Problem/Motivation

In 🐛 Missing url prefix on language neutral content Fixed we ensured that all language-neutral content still had a language prefix so the interface language was correct.

Then in 🐛 Language negotiation breaks updating Drupal 9 to 10 Needs work we discovered that this is not always desired, because some URLs explicitly should not have a language prefix

However, in the case that an entity has LANGCODE_NOT_APPLICABLE we probably still want links generated to that entity to have the correct interface language.

This issue is to decide whether that is the case, and if so, how we achieve it. See #3385550-14: Language negotiation breaks updating Drupal 9 to 10 → for previous discussion.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

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