The default original strings of a navigation block could get populated by another installed language

Problem/Motivation

During today's usability meeting (#3436905: Drupal Usability Meeting 2024-04-05) we've noticed the following potential issue with navigation block titles in the context of multilingual - basically english original strings get populated with spanish strings (see steps to reproduce for more details).

For the record, the attendees at the usability meeting were @AaronMcHale, @benjifisher, @rkoller, @shaal, @simohell, @skaught, and @worldlinemine.

Steps to reproduce

1. Install a new site with demo_umami
2. take a look at /admin/config/user-interface/navigation-block
3. Go to /admin/config/regional/language and activate account administration pages
4. Now go to the edit user page on /en/user/1/edit
5. Switch the admin language to spanish
6. Go again to /admin/config/user-interface/navigation-block
7. Press the place navigation block button
8. Place the contenido navigation block
9. returning on the overview page after placing the navigation block you now have two contenido navigation blocks in the sidebar, while in the list on the overview page (/admin/config/user-interface/navigation-block) you have one contenido and one content navigation block listed. if you save the page both blocks are called contenido now
10. switch the account administration pages back to english on /user/1/edit
11. return another time to /en/admin/config/user-interface/navigation-block

the sidebar shows two content blocks (correctly displayed in english). but all the titles on the navigation block overview page are shown in spanish now. if you click "translate" for each of the contenido blocks you notice the newly added block shows spanish as the original, but the one added per default has english as the original language. if you click the edit button for the english original it has contenido as its english title as well.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes