How to exclude specific languages from l10n_update?

Problem/Motivation

Large multilang projects often have languages enabled, which are not relevant for interface translation, just for content translation.
Still the language update functionality (former l10n_update) in core fetches them or you manually have to uncheck the language each time a language update is performed.

Is there any way to disable interface translation updates for certain languages?

I'm creating this as support request first, but if there's no way yet, it should be transformed into a feature request to have a checkbox for this in the language settings.

Steps to reproduce

1. Enable several languages, which you need for content translation
2. See them listed at /admin/reports/translations and all checked by default and reported they need an update in the status report
3. Don't be able to switch the updates off for languages, which are never used in the admin area but fill up the database

For 5 languages only, the l10n_update process already takes minutes.

Proposed resolution

Add a setting to include (or exclude) languages from l10n.
I'd expect such a setting at
/admin/config/regional/translate/settings
or
/admin/config/regional/language

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet