This refactors and fixes unicode issues where entities don't display
properly due to being a special character that seems to be rendered
incorrectly in a non-deterministic way every time.
This either removes aria-hidden=true assignments from buttons with
text, or adds a span to only hide the 'x' symbol rather than the
button for closing buttons.
Change the remaining "Admin settings" with a button, namely
changing a stream's privacy, to instead be a "[Change]" link
opening a confirmation modal.
Fixes: #3493.