Add support for Terms Query Pagination blocks

[jillro]

Introduce new blocks to enable pagination for terms queries, including "Previous", "Next", and "Page Numbers" links.

Adds build_terms_query_vars_from_block() and terms_query_register_query_vars() to wp-includes/blocks.php to support pagination in the Terms Query block.

These helper functions are used by:

• The updated Term Template block (which now supports paginated term results via the termspage query variable)
• The new Terms Query Pagination blocks (core/terms-query-pagination, core/terms-query-pagination-next, core/terms-query-pagination-previous, core/terms-query-pagination-numbers)

build_terms_query_vars_from_block() extracts and normalizes query arguments from the block context, handling both inherited (taxonomy archive) and custom term queries. It follows the same pattern as the existing build_query_vars_from_query_block() and build_comment_query_vars_from_block().

terms_query_register_query_vars() registers termspage as a public query variable so it can be used for pagination URLs.

The block files themselves (block.json, index.php, CSS, JS) are synced automatically via the Gutenberg build process.

[audrasjb]

Removing trunk version as this is not going to be shipped with WP 7.0 but in the next releases.

[desrosj]

Since this is an enhancement, there's no first version of WordPress this can be reproduced in. Removing trunk version.

@jillro Thanks for opening PRs for both code bases! At quick glance, the version within the @since annotations will need to be bumped to 7.1.0 now. It's possible some more changes will be required, so worth refreshing both PRs so that they're ready for consideration with 7.0 being released in the next 24 hours.

Just ​linking to the corresponding Gutenberg PR for easy reference.

[jillro]

Thanks @desrosj, I've bumped the @since annotations to 7.1.0 in both PRs and refreshed Gutenberg PR against trunk.

One change worth noting on the core side: the termspage query variable is no longer registered via a query_vars filter helper. It's now added straight to WP::$public_query_vars in wp-includes/class-wp.php, with coverage added in tests/phpunit/tests/query/vars.php.

Both PRs should be ready for another look for 7.1.0 consideration. Happy to make any further adjustments.