Allow admins the option to show the header language switcher even for logged-in users

[nat (Natalie T)]

Currently, the site setting content localization anon language switcher is a toggle to show the language switcher only for non-logged-in users.

Screenshots 📸

The Setting

The Switcher

There have been some requests to expand this to allow logged-in users to set the language from the header as well.

The work here would involve

• updating the setting name to exclude “anon”
• expanding the setting to “none”, “anonymous”, “all”

• the anon language is tracked via cookies, switching the language in logged-in should update the user.locale instead of cookies

By completing this, we should also update related topics (e.g. Header Locale Selector) that this is now possible in core.