[UX] Add a 'visible' property to display modes

Describe your issue or idea

There are several interfaces in core where we allow people to choose a display mode to view (for example: in the Views UI, soon: reference field formatters, soon: node previews). In these places non-viewable view modes like RSS, Search-index, and Search result highlighting input appear as options, and they should not.

We need a way to filter them out so that these user interfaces contain only options that can actually be viewed.

Steps to reproduce (if reporting a bug)

• build a view of posts

Actual behavior (if reporting a bug)

• see the "Search index" display mode

Expected behavior (if reporting a bug)

• the "Search index" display mode should not be visible here