[terra-status-view] Remove opt object and add proptype check

[yuderekyu]

Feature Request

We export variants with Statusview.opts.variants, let's remove the opts object, create a named export, and add a proptype check.

const StatusViewVariants = {
  NODATA: 'no-data',
  NOMATCHINGRESULTS: 'no-matching-results',
  NOTAUTHORIZED: 'not-authorized',
  ERROR: 'error',
  CUSTOM: 'custom',
};

variant: PropTypes.string.onOf([ 'no-data', 'no-matching-results', etc]);
...
...
export default StatusView;
export {StatusViewVariants}