Problem/Motivation
Local task labels are always displayed using the content language, ignoring that users can set their admin language preference (if the site has an admin language preference option set in negotiation). Local task label should honor this config and use the admin interface language. Even if they are in a non-admin pages, they are part of the admin interface.
This is very similar to what is being done in #2313309: Admin toolbar and contextual links should always be rendered in the admin language (if set), but for local tasks. It's worth to note that in that issue current patches seems to translate Contextual Links as well (if not, probably a new issue should be created).
Proposed resolution
Render local task labels using the admin language config from language negotiation.
Remaining tasks
Implement it.
User interface changes
Local task labels will be in an admin-appropriate language. Optionally, a checkbox can be added to make this behavior optional.
API changes
Likely none.
