Query Pagination: add an empty wrapper when at first/last page

[MaggieCabrera]

Description

Fixes #34997

To keep the alignments consistent between pages and between the editor and the frontend, I've added an empty wrapper (right now it's a simple span to test the fix, I can add the rest of the wrapper attributes and/or change it to an anchor depending on discussion).

How has this been tested?

I've used the following markup on emptytheme, tested with inherit set to true and false:

<!-- wp:query {"queryId":13,"query":{"perPage":"5","pages":0,"offset":0,"postType":"post","categoryIds":[],"tagIds":[],"order":"desc","orderBy":"date","author":"","search":"","exclude":[],"sticky":"","inherit":false},"displayLayout":{"type":"list"}} -->
<div class="wp-block-query"><!-- wp:post-template -->
<!-- wp:post-title {"isLink":true} /-->

<!-- wp:post-excerpt /-->
<!-- /wp:post-template -->

<!-- wp:query-pagination {"layout":{"type":"flex","justifyContent":"space-between"}} -->
<!-- wp:query-pagination-previous /-->

<!-- wp:query-pagination-numbers /-->

<!-- wp:query-pagination-next /-->
<!-- /wp:query-pagination --></div>
<!-- /wp:query -->

Adapt your site or your query block so the pagination shows up and navigate to the first and last pages of the loop. The numbers should stay in the center.

Screenshots

Editor:

First page:

Before	After

Last page:

Before	After

Types of changes

Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[MaggieCabrera]

It could be interesting to keep the label as a disabled element so that it maintains its size and keeps the numbers centered and always in the same position regardless of the page you are in.

[MaggieCabrera]

The empty div was moving the numbers between pages, so I went with placeholders for the text and added classes for the first/last pages in case the theme devs want to hide these. We could add visibility:hidden to these or lower the opacity. I'd love to hear any input on this approach.

Before:

After:

Above is TT2

[carolinan]

My test installation has 4 posts.

When I apply the PR and enable Empty theme, Twenty Twenty-Two or Blockbase I see the following on the front:
Notice: Undefined variable: wp_query in blocks/query-pagination-next.php on line 30 Notice: Trying to get property 'max_num_pages' of non-object in blocks/query-pagination-next.php on line 30