DAC: Unique and descriptive labels for repeatable buttons

[bryophyta]

Some kinds of buttons can occur multiple times on a single page, e.g.:

• show and hide buttons on containers on Fronts pages
• +1 and -1 buttons

Users who are navigating the page in a non-contextual mode will just see the same labels repeated for different instances of the buttons. It was recommended that we find a way of attaching more information to the labels for these buttons, to add context for non-contextual navigation. (E.g. hide Opinion section?)

(Closely related to #5335 )