Convert tabbedview to functional component (#12478)
* Convert tabbedview to functional component
The 'Tab' is still a class, so now it's a functional component that
has a supporting class, which is maybe a bit... jarring, but I think
is actually perfectly logical.
* put comment back
* Fix bad tab ID behaviour
* Change to sub-components
and use contitional call syntax
* Comments
* Fix element IDs
