message: Add test selectors to simple-paginator
diff: {{#if hasPages}}
  <span local-class='SimplePaginator__element'>
  - {{#bs-button disabled=(not hasPrev) onClick=(action previousPage)}}
  + {{#bs-button data-test-previous-page-button disabled=(not hasPrev) onClick=(action previousPage)}}
  <span aria-label="{{t 'paginator.previous'}}">
  &lt;
  </span>
  {{t 'paginator.page' page=curPage max=maxPage}}
  </span>
  <span local-class='SimplePaginator__element'>
  - {{#bs-button disabled=(not hasNext) onClick=(action nextPage)}}
  + {{#bs-button data-test-next-page-button disabled=(not hasNext) onClick=(action nextPage)}}
  <span aria-label="{{t 'paginator.previous'}}">
  &gt;
  </span>
  