Block Editor: Use a proper component for the replacement taxonomy term meta box

[johnbillion]

If a taxonomy is registered with a custom meta box type, for example radio, then when you're using the block editor the taxonomy meta box component just gets removed and replaced with a server-side meta box.

Now that the APIs for Gutenberg are relatively stable, Extended CPTs should introduce its own taxonomy term meta box React components and use those in the block editor instead.

This library looks like it will be very helpful: https://github.com/helgatheviking/Radio-Buttons-for-Taxonomies